Glossary

A

abend

See abnormal end of task.

abend reason code

A 4-byte hexadecimal code that uniquely identifies a problem with DB2 UDB for OS/390.

abnormal end of task (abend)

In DB2 UDB for OS/390, the termination of a task, job, or subsystem because of an error condition that recovery facilities cannot resolve during execution.

abnormal termination

(1) A system failure or operator action that causes a job to end unsuccessfully.

(2) In DB2, exits that are not under program control, such as a trap or segv.

absolute path

The full path name of an object. Absolute path names begin at the highest level, or "root" directory (which is identified by the forward slash (/) or back slash (\) character).

access function

A user-provided function that converts the data type of text stored in a column to a type that can be processed by the Text Extender.

access method services

A facility that is used to define and reproduce VSAM key-sequenced data sets.

access path

(1) The method that is selected by the optimizer for retrieving data from a specific table. For example, an access path can involve the use of an index, a sequential scan, or a combination of the two.

(2) The path that is used to locate data that is specified in SQL statements. An access path can be indexed or sequential.

access plan

The set of access paths that are selected by the optimizer to evaluate a particular SQL statement. The access plan specifies the order of operations to resolve the execution plan, the implementation methods (such as JOIN), and the access path for each table referenced in the statement.

accounting string

User-defined accounting information that is sent to DRDA servers by DB2 Connect. This information can be specified at one of these locations:

The client workstation using the SQLESACT API or the DB2ACCOUNT environment variable
The DB2 Connect workstation using the DFT_ACCOUNT_STR database manager configuration parameter.

active log

(1) In DB2 UDB, the primary and secondary log files that are currently needed for recovery and rollback. Contrast with archive log.

(2) The portion of the DB2 UDB for OS/390 log to which log records are written as they are generated. The active log always contains the most recent log records, whereas the archive log holds records that are older and no longer fit on the active log.

adjacent nodes

Two nodes connected by at least one path that connects no other nodes.

administrative authority

A level of authority that gives a user privileges over a set of objects. For example, DBADM authority gives privileges over all objects in a database, and SYSADM authority gives privileges over all objects in a system.

administrative support table

A table that is used by a DB2 extender to process user requests on image, audio, and video objects. Some administrative support tables identify user tables and columns that are enabled for an extender. Other administrative support tables contain attribute information about objects in enabled columns. Also called a metadata table.

ADSM

See Tivoli Storage Manager.

Advanced Peer-to-Peer Networking (APPN)

An extension to SNA that features distributed network control, dynamic definition of network resources, and automated resource registration and directory lookup.

Advanced Peer-to-Peer Networking (APPN) network

A collection of interconnected network nodes and their client end nodes.

Advanced program-to-program communication (APPC)

The general facility that characterizes the LU 6.2 architecture and its various implementations in products.

after-image

In DB2 replication, the updated content of a source table element that is recorded in a change data table or in a database log or journal. Contrast with before-image.

agent

(1) A separate process or thread that carries out all DB2 requests that are made by a particular client application.

(2) In DB2 UDB for OS/390, the structure that associates all processes that are involved in a DB2 UDB for OS/390 unit of work. An allied agent is generally synonymous with an allied thread. System agents are units of work that process independently of the allied agent, such as prefetch processing, deferred writes, and service tasks.

agent site

In the Data Warehouse Center, the location, defined by a single network host name, where an agent application is installed.

aggregate function

Synonym for column function.

alert

An action, such as a beep or warning, that is generated when a performance variable exceeds or falls below its warning or alarm threshold.

alias

An alternative name used to identify a table, view, database, or nickname. An alias can be used in SQL statements to refer to a table or view in the same DB2 subsystem or a remote DB2 subsystem.

alias chain

A series of table aliases that refer to each other in a sequential, nonrepeating fashion.

allied address space

In DB2 UDB for OS/390, an area of storage that is external to and connected to DB2 UDB for OS/390. An allied address space is capable of requesting DB2 UDB for OS/390 services.

allied thread

A thread that originates at the local DB2 UDB for OS/390 subsystem and that can access data at a remote DB2 UDB for OS/390 subsystem.

allocated cursor

In DB2 UDB for OS/390, a cursor that is defined for stored procedure result sets by using the SQL statement ALLOCATE CURSOR.

already verified

An LU 6.2 security option that allows DB2 UDB for OS/390 to provide the user's verified authorization ID when allocating a conversation. The user is not validated by the partner subsystem.

ambiguous cursor

(1) A cursor that cannot be determined to be updatable or read-only from its definition or context.

(2) In DB2 UDB for OS/390, a database cursor that is not defined with the FOR FETCH ONLY clause or the FOR UPDATE OF clause, is not defined on a read-only result table, is not the target of a WHERE CURRENT clause on an SQL UPDATE or DELETE statement, and is in a plan or package that contains either PREPARE or EXECUTE IMMEDIATE SQL statements.

APF

See authorized program facility.

API

See application programming interface.

APPC

See advanced program-to-program communication.

APPL

A VTAM network definition statement that is used to define DB2 UDB for OS/390 to VTAM as an application program that uses SNA LU 6.2 protocols.

application

A program or set of programs that performs a task; for example, a payroll application.

application ID

A string that uniquely identifies an application across networks. An ID is generated at the time that the application connects to the database. This ID is known on both the client and the server and can be used to correlate the two parts of the application.

application plan

The control structure that is produced during the bind process. DB2 UDB for OS/390 uses the application plan to process SQL statements that it encounters during statement execution.

application process

The unit to which resources and locks are allocated. An application process involves the running of one or more programs.

application programming interface (API)

(1) A functional interface supplied by the operating system or by a separately orderable licensed program. An API allows an application program that is written in a high-level language to use specific data or functions of the operating system or the licensed programs.

(2) In DB2, a function within the interface, for example, the get error message API.

application requester

A facility that accepts a database request from an application process and passes it to an application server.

application server

The local or remote database manager to which the application process is connected.

Apply program

In DB2 replication, a program that is used to refresh or update a target table, depending on the applicable source-to-target rules. Contrast with Capture program and Capture trigger.

Apply qualifier

In DB2 replication, a character string that identifies subscription definitions that are unique to each instance of the Apply program.

APPN

See Advanced Peer-to-Peer Networking

archive log

(1) The set of log files that are closed and are no longer needed for normal processing. These files are retained for use in roll-forward recovery. Contrast with active log.

(2) The portion of the DB2 UDB for OS/390 log that contains log records that are copied from the active log.

argument

A value passed to or returned from a function or procedure at run time.

asynchronous

Without regular time relationship; unexpected and unpredictable with respect to the processing of program instructions. Contrast with synchronous.

asynchronous batched update

A process in which all changes to the source are recorded and applied to existing target data at specified intervals. Contrast with asynchronous continuous update.

asynchronous continuous update

A process in which all changes to the source are recorded and applied to existing target data after being committed in the base table. Contrast with asynchronous batched update.

attach

In DB2, to remotely access objects at the instance level.

attachment facility

An interface between DB2 UDB for OS/390 and TSO, IMS, CICS, or batch address spaces. An attachment facility allows application programs to access DB2 UDB for OS/390.

attribute

In SQL database design, a characteristic of an entity. For example, the phone number of an employee is one of that employee's attributes.

authority

See administrative authority.

authorization ID

(1) A character string in a statement that designates a set of privileges. It is used by the database manager for authorization checking and as an implicit qualifier for the names of objects such as tables, views, and indexes.

(2) A string that can be verified for connection to DB2 UDB for OS/390 and to which a set of privileges is allowed. An authorization ID can represent an individual, an organizational group, or a function, but DB2 UDB for OS/390 does not determine this representation.

authorized program facility (APF)

In DB2 UDB for OS/390, a facility that permits the identification of programs that are authorized to use restricted functions.

autocommit

To automatically commit the current unit of work after each SQL statement.

automatic rebind

(1) A feature that automatically rebinds an invalidated package without requiring a bind command to be entered manually or a bind file to be present.

(2) In DB2 UDB for OS/390, a process by which SQL statements are bound automatically (without a user issuing a BIND command) when an application process begins execution and the bound application plan or package it requires is not valid. See also bind.

auxiliary index

In DB2 UDB for OS/390, an index on an auxiliary table in which each index entry refers to an LOB.

auxiliary table

In DB2 UDB for OS/390, a table that stores columns outside the table in which they are defined. Contrast with base table.

B

backup pending

The state of a database or table space that prevents an operation from being performed until the database or table space is backed up.

backward log recovery

The fourth and final phase of restart processing during which DB2 UDB for OS/390 scans the log in a backward direction to apply UNDO log records for all aborted changes.

base aggregate table

In DB2 replication, a type of target table that contains data aggregated from a source table or a point-in-time table at intervals.

base table

(1) A table created with the CREATE TABLE statement. Such a table has both its description and data physically stored in the database. Contrast with view.

(2) In DB2 UDB for OS/390: (a) A table that is created by the SQL CREATE TABLE statement and that holds persistent data. Contrast with result table and temporary table. (b) A table that contains an LOB column definition. The actual LOB column data is not stored with the base table. The base table contains a row ID for each row and an indicator column for each of its LOB columns. Contrast with auxiliary table.

base table space

In DB2 UDB for OS/390, a table space that contains base tables.

basic conversation

An LU 6.2 conversation between two transaction programs using the APPC basic conversation API. Contrast with mapped conversation.

basic predicate

A predicate that compares two values.

basic sequential access method (BSAM)

An access method that DB2 UDB for OS/390 uses for storing or retrieving data blocks in a continuous sequence, using either a sequential access or a direct access device.

before-image

In DB2 replication, the content of a source table column prior to a refresh, as recorded in a change data table or in a database log or journal. Contrast with after-image.

before trigger

In DB2 UDB for OS/390, a trigger that is defined with the trigger activation time BEFORE.

binary integer

A basic data type that can be further classified as small integer or large integer.

binary large object (BLOB)

A sequence of bytes with a size ranging from 0 bytes to 2 gigabytes. This string does not have an associated code page and character set. Image, audio, and video objects are stored in BLOBs. Compare to character large object (CLOB).

binary string

In DB2 UDB for OS/390, a sequence of bytes that is not associated with a CCSID. For example, the BLOB data type is a binary string.

bind

(1) In SQL, the process by which the output from the SQL precompiler is converted to a usable structure called an access plan. During this process, access paths to the data are selected and some authorization checking is performed.

(2) In DB2 UDB for OS/390, the process by which the output from the DBMS precompiler is converted to a usable control structure (which is called a package or an application plan). During the process, access paths to the data are selected and some authorization checking is performed. See also automatic rebind, dynamic bind, incremental bind, static bind.

bindery object name

A 48-byte character string that contains the name of a bindery object on the NetWare file server. The database manager configuration field, objectname, uniquely represents a DB2 server instance, and is stored as an object in the bindery on a NetWare file server.

bind file

A file produced by the precompiler when the bind command or API is used with the BINDFILE option. This file includes information about all SQL statements in the application program.

bit data

Data with character type CHAR or VARCHAR that is not associated with a coded character set and therefore is never converted.

BLOB

See binary large object.

block

A string of data elements recorded or transmitted as a unit.

blocking

An option that is specified when binding an application. It allows caching of multiple rows of information by the communications subsystem so that each FETCH statement does not require the transmission of one row for each request across the network. Contrast with data blocking.

bootstrap data set (BSDS)

A VSAM data set that contains name and status information for DB2 UDB for OS/390, as well as RBA range specifications, for all active and archive log data sets. It also contains passwords for the DB2 UDB for OS/390 directory and catalog, and lists of conditional restart and checkpoint records.

broadcast join

A join in which all partitions of a table are sent to all nodes.

browser

A Text Extender function that enables you to display text on a computer monitor.

BSAM

See basic sequential access method.

BSDS

See bootstrap data set.

buffer pool

In DB2 UDB for OS/390, main storage that is reserved to satisfy the buffering requirements for one or more table spaces or indexes.

built-in function

An SQL function that is provided by DB2 and appears in the SYSIBM schema. Contrast with user-defined function.

business metadata

Data that describes information assets in business terms. Business metadata is stored in the information catalog and accessed by users to find and understand the information they need. For example, business metadata for a program would contain a description of what the program does and what tables it uses. Contrast with technical metadata.

business name

In the Data Warehouse Center, a name that refers to a step. Each step has a business name and a DB2 table name that is associated with the step. Business names are generally used by warehouse users; DB2 table names are used in SQL statements.

byte reversal

A technique in which numeric data is stored with the least significant byte first.

C

cache

A buffer that contains frequently accessed instructions and data; it is used to reduce access time.

Cache Manager

In Net.Data, the program that manages a cache for one workstation. The Cache Manager can manage multiple caches.

cache structure

A coupling facility structure that stores data that can be available to all members of a Parallel Sysplex. A DB2 UDB for OS/390 data sharing group uses cache structures as group buffer pools.

caching

The process of storing frequently used results from a request to the Web server locally for quick retrieval, until it is time to refresh the information.

CAF

See call attachment facility.

call attachment facility (CAF)

A DB2 UDB for OS/390 attachment facility for application programs that run in TSO or MVS batch. The CAF is an alternative to the DSN command processor and provides greater control over the execution environment.

call level interface (CLI)

A callable API for database access, which is an alternative to an embedded SQL API. In contrast to embedded SQL, the CLI does not require precompiling or binding by the user, but instead provides a standard set of functions to process SQL statements and related services at run time.

Capture program

In DB2 replication, a program that reads database log or journal records to capture data about changes made to DB2 source tables. Contrast with Apply program and Capture trigger.

Capture trigger

In DB2 replication, a mechanism that captures delete, update, and insert operations performed on non-IBM source tables. Contrast with Capture program and Apply program.

cardinality

The number of rows in a database table.

cascade

In the Data Warehouse Center, to run a sequence of events. When a step cascades to another step, the steps run sequentially or concurrently. A step can also cascade to a program, which runs after the step finishes running.

cascade delete

The way in which DB2 UDB for OS/390 enforces referential constraints when it deletes all descendent rows of a deleted parent row.

cascade rejection

In DB2 replication, the process of rejecting a replication transaction because it is associated with a transaction that had a conflict detected and was itself rejected.

CASE expression

In DB2 UDB for OS/390, an expression that allows another expression to be selected based on the evaluation of one or more conditions.

cast function

A function used to convert instances of a data type (origin) into instances of a different data type (target). In general, cast functions have the name of the target data type. They have a single argument whose type is the origin data type; their return type is the target data type.

catalog

A set of tables and views maintained by the database manager. These tables and views contain information about the database, such as descriptions of tables, views, and indexes.

catalog node

The node at which the catalog tables reside. The catalog node can be a different node for each database.

catalog table

Any table in the DB2 UDB for OS/390 catalog.

catalog view

A view of a system table created by the Text Extender for administration purposes. A catalog view contains information about the tables and columns that are enabled for use by the Text Extender.

CCD table

See consistent-change-data table.

CCSID

See coded character set identifier.

CDB

See communications database.

CDRA

See Character Data Representation Architecture.

CD table

See change data table.

CEC

Central electronic complex. See central processor complex.

central processor complex (CPC)

A physical collection of hardware (such as an ES/3090) that consists of main storage, one or more central processors, timers, and channels.

CFRM policy

In DB2 UDB for OS/390, a declaration by an MVS administrator regarding the allocation rules for a coupling facility structure.

change aggregate table

In DB2 replication, a type of target table that contains data aggregations based on changes recorded for a source table.

change data (CD) table

A replication control table at the source server that contains changed data for a replication source table.

Character Data Representation Architecture (CDRA)

An architecture used to achieve consistent representation, processing, and interchange of string data.

character large object (CLOB)

A sequence of characters (single-byte, multibyte, or both) up to 2 gigabytes. A CLOB can be used to store large text objects. Also called character large object string. Compare to binary large object (BLOB).

character string

A sequence of bytes or characters.

character string delimiter

The characters used to enclose character strings in delimited ASCII files that are imported or exported. See delimiter.

CHECK clause

In SQL, an extension to the SQL CREATE TABLE and SQL ALTER TABLE statements that specifies a table check constraint.

check condition

A restricted form of search condition used in check constraints.

check constraint

A constraint that specifies a check condition that is not false for each row of the table on which the constraint is defined.

check integrity

In DB2 UDB for OS/390, the condition that exists when each row in a table conforms to the table check constraints that are defined on that table. Maintaining check integrity requires DB2 UDB for OS/390 to enforce table check constraints on operations that add or change data.

check pending

A state into which a table can be put where only limited activity is allowed on the table and constraints are not checked when the table is updated.

checkpoint

A point at which DB2 UDB for OS/390 records internal status information on the log; the recovery process uses this information if the subsystem abnormally terminates.

CI

See control interval.

CICS

An IBM licensed program that provides online transaction-processing services and management for critical business appliations. In DB2 UDB for OS/390 information, this term represents the following products:

CICS Transaction Server for OS/390: Customer Information Control Center Transaction Server for OS/390

CICS/ESA: Customer Information Control System/Enterprise Systems Architecture

CICS/MVS: Customer Information Control System/Multiple Virtual Storage

CICS attachment facility

A DB2 UDB for OS/390 subcomponent that uses the MVS subsystem interface (SSI) and cross storage linkage to process requests from CICS to DB2 UDB for OS/390 and to coordinate resource commitment.

CIDF

See control interval definition field.

circular log

A database log in which records are overwritten if they are no longer needed by an active database. Consequently, if a failure occurs, lost data cannot be restored during forward recovery. Contrast with recoverable log.

claim

In DB2 UDB for OS/390, a notification to the DBMS that an object is being accessed. Claims prevent drains from occurring until the claim is released, which usually occurs at a commit point. See also drain.

claim class

In DB2 UDB for OS/390, a specific type of object access that can be one of the following types: cursor stability (CS), repeatable read (RR), write.

claim count

In DB2 UDB for OS/390, a count of the number of agents that are accessing an object.

class of service

In DB2 UDB for OS/390, a VTAM term for a list of routes through a network, arranged in an order of preference for their use.

clause

In DB2 UDB for OS/390 SQL, a distinct part of a statement, such as a SELECT clause or a WHERE clause.

cleanse

The process of manipulating the data extracted from operational systems so as to make it usable by the data warehouse.

CLI

See call level interface.

client

(1) Any program (or workstation that it is running on) that communicates with and accesses a database server.

(2) See requester.

cliette

A long-running process in Net.Data Live Connection that serves requests from the Web server. The Connection Manager schedules cliette processes to serve these requests.

CLIST

Command list. A language that DB2 UDB for OS/390 uses to perform TSO tasks.

CLOB

See character large object.

CLP

See Command Line Processor.

CLPA

See create link pack area.

clustered index

An index whose sequence of key values closely corresponds to the sequence of rows stored in a table. The degree to which this correspondence exists is measured by statistics that are used by the optimizer.

coded character set

A set of unambiguous rules that establishes a character set and the one-to-one relationships between the characters of the set and their coded representations.

coded character set identifier (CCSID)

A number that includes an encoding scheme identifier, character set identifiers, code page identifiers, and other information that uniquely identifies the coded graphic character representation.

code page

A set of assignments of characters to code points.

code point

In CDRA, a unique bit pattern that represents a character in a code page.

code set

Encoding values for a character set that provides the interface between the system and its input and output devices. ISO uses code set as the term equivalent to the IBM-defined term code page.

cold start

(1) The process of starting a system or program using an initial program load procedure. Contrast with warm start.

(2) A process by which DB2 UDB for OS/390 restarts without processing any log records.

collating sequence

The sequence in which the characters are ordered for the purpose of sorting, merging, comparing, and processing indexed data sequentially.

collection

In DB2 UDB for OS/390, a group of packages that have the same qualifier.

collocated join

The result of two tables being joined in which the following conditions are met:

The tables reside in a single-partition nodegroup in the same database partition; or they are in the same partitioned nodegroup and have the same number of partitioning columns, the columns are partition-compatible, and both tables use the same partitioning function.
All pairs of the corresponding partitioning key columns participate in the equijoin predicates.

column distribution value

Statistics describing the most frequent values of some column or the quantile values. These values are used in the optimizer to help determine the best access plan.

column function

(1) An operation used in queries that applies to the values from several rows. Column functions include SUM, AVG, MIN, MAX, COUNT, STDDEV, and VARIANCE. Synonym for aggregate function.

(2) In DB2 UDB for OS/390, an SQL operation that derives its result from a collection of values across one or more rows. Contrast with scalar function.

"come from" checking

An LU 6.2 security option that defines a list of authorization IDs that are allowed to connect to DB2 UDB for OS/390 from a partner LU.

command

A DB2 UDB for OS/390 operator command or a DSN subcommand. A command is distinct from an SQL statement.

Command Line Processor (CLP)

A character-based interface for entering SQL statements and database manager commands.

command prefix

In DB2 UDB for OS/390, a one- to eight-character command identifier. The command prefix distinguishes the command as belonging to an application or subsystem rather than to OS/390.

command recognition character (CRC)

A character that permits an MVS console operator or an IMS subsystem user to route DB2 commands to specific DB2 UDB for OS/390 subsystems.

command scope

In DB2 UDB for OS/390, the scope of command operation in a data sharing group. If a command has member scope, the command displays information only from the one member or affects only non-shared resources that are owned locally by that member. If a command has group scope, the command displays information from all members, affects non-shared resources that are owned locally by all members, displays information on sharable resources, or affects sharable resources.

commit

The operation that ends a unit of work by releasing locks so that the database changes made by that unit of work can be perceived by other processes. This operation makes the data changes permanent.

commitment control

The establishment of a boundary within the process under which Net.Data is running, where operations on resources are part of a unit of work.

commit point

A point in time when data is considered to be consistent. Synonym for point of consistency.

committed phase

In DB2 UDB for OS/390, the second phase of the multi-site update process that requests all participants to commit the effects of the logical unit of work.

common-index table

A DB2 table whose text columns share a common text index. See also multi-index table.

Common Programming Interface Communications (CPI-C)

An API for applications that require program-to-program communication, using SNA LU 6.2 to create a set of interprogram services.

common service area (CSA)

In OS/390, a part of the common area that contains data areas that can be addressed by all address spaces.

common table expression

An expression that defines a result table with a name (qualified SQL identifier) that can be specified as a table name in any FROM clause in the fullselect that follows the WITH clause.

communications database (CDB)

A set of tables in the DB2 UDB for OS/390 catalog that are used to establish conversations with remote database management systems.

comparison operator

An infix operator used in comparison expressions. Comparison operators are ¬< (not less than), <= (less than or equal to), ¬= (not equal to), = (equal to), >= (greater than or equal to), > (greater than), and ¬> (not greater than).

complete

A table attribute that indicates that the table contains a row for every primary key value of interest. As a result, a complete source table can be used to perform a refresh of a target table.

complete CCD table

A CCD table that contains all the rows that satisfy the source view and predicates from the source table or view. Contrast with noncomplete CCD table.

composite key

An ordered set of key columns of the same table.

compound SQL statement

A block of SQL statements that are executed in a single call to the application server.

compression dictionary

In DB2 UDB for OS/390, the dictionary that controls the process of compression and decompression. This dictionary is created from the data in the table space or table space partition.

concurrency

The shared use of resources by multiple interactive users or application processes at the same time.

condensed

A table attribute indicating that the table contains current data rather than a history of changes to the data. A condensed table includes no more than one row for each primary key value in the table. As a result, a condensed table can be used to supply current information for a refresh.

condensed CCD table

In DB2 replication, a CCD table that contains only the most current value for a row. This type of table is useful for staging changes to remote locations and for summarizing hot-spot updates. Contrast with noncondensed CCD table.

conditional restart

A DB2 UDB for OS/390 restart that is directed by a user-defined conditional restart control record (CRCR).

conflict detection

In update-anywhere replication configurations:

The process of detecting constraint errors.
The process of detecting if the same row was updated in the source and target tables during the same replication cycle. When a conflict is detected, the transaction that caused the conflict is rejected. See also enhanced conflict detection, standard conflict detection, and row-replica conflict detection.

connect

In DB2, to access objects at the database level.

connection

(1) An association between an application process and an application server.

(2) In data communications, an association established between functional units for conveying information.

(3) In SNA, the existence of a communication path between two partner LUs that allows information to be exchanged (for example, two DB2 UDB for OS/390 subsystems that are connected and communicating by way of a conversation).

connection handle

Within the CLI, the data object that contains information associated with a connection. This information includes general status information, transaction status, and diagnostic information.

connection ID

In DB2 UDB for OS/390, an identifier that is supplied by the attachment facility and that is associated with a specific address space connection.

Connection Manager

An executable file, dtwcm, in Net.Data that is needed to support Live Connection.

consistency token

In DB2 UDB for OS/390, a timestamp that is used to generate the version identifier for an application.

consistent-change-data (CCD) table

In DB2 replication, a type of target table that is used for auditing or staging data or both. See also complete CCD table, condensed CCD table, external CCD table, internal CCD table, noncomplete CCD table, and noncondensed CCD table.

constant

A language element that specifies an unchanging value. Constants are classified as string constants or numeric constants. Contrast with variable.

constraint

A rule that limits the values that can be inserted, deleted, or updated in a table. See check constraint, referential constraint, and unique constraint.

container

See table space container.

contention

In the database manager, a situation in which a transaction attempts to lock a row or table that is already locked.

Control Center

A graphical interface that shows database objects (such as databases and tables) and their relationship to each other. From the Control Center, you can perform the tasks provided by the DBA Utility, Visual Explain, and Performance Monitor tools. Contrast with DataJoiner Replication Administration (DJRA) tool.

control interval (CI)

In VSAM, a fixed-length area of direct access storage in which VSAM stores records and creates distributed free space. Also, in a key-sequenced data set or file, the set of records pointed to by an entry in the sequence-set index record. The control interval is the unit of information that VSAM transmits to or from direct access storage. A control interval always includes an integral number of physical records.

control interval definition field (CIDF)

In VSAM, a field located in the 4 bytes at the end of each control interval; it describes the free space, if any, in the control interval.

control metadata

In the Data Warehouse Center, information about changes to the warehouse, such as the date and time that a table is updated by the processing of a step.

control point

(1) In APPN, a component of a node that manages resources of that node and optionally provides services to other nodes in the network. Examples are a system services control point (SSCP) in a type 5 node, a physical unit control point (PUCP) in a type 4 node, a network node control point (NNCP) in a type 2.1 (T2.1) network node, and an end node control point (ENCP) in a T2.1 end node. An SSCP and an NNCP can provide services to other nodes.

(2) A component of a T2.1 node that manages the resources of that node. If the T2.1 node is an APPN node, the control point is capable of engaging in control point-to-control point sessions with other APPN nodes. If the T2.1 node is a network node, the control point also provides services to adjacent end nodes in the T2.1 network. See also physical unit.

control privilege

The authority to completely control an object. This includes the authority to access, drop, or alter an object, and the authority to extend or revoke privileges on the object to other users.

control server

In DB2 replication, the database location of the applicable subscription definitions and Apply program control tables.

control table

In DB2 replication, a table in which replication source and subscription definitions or other replication control information is stored.

conversation

In APPC, a connection between two transaction programs over a logical unit-logical unit (LU-to-LU) session that allows them to communicate with each other while processing a transaction.

conversational transaction

In APPC, two or more programs communicating using the services of logical units (LUs).

conversation security

In APPC, a process that allows validation of a user ID or group ID and password before establishing a connection.

conversation security profile

The set of user IDs or group IDs and passwords that are used by APPC for conversation security.

Coordinated Universal Time (UTC)

Synonym for Greenwich Mean Time.

coordinating agent

The agent that is started when a request is received by the database manager from an application. It remains associated with the application during the life of the application. This agent coordinates subagents that work for the application. See also subagent.

coordinator

In DB2 UDB for OS/390, the system component that coordinates the commit or rollback of a unit of work that includes work that is done on one or more other systems.

coordinator node

The node to which the application originally connected and on which the coordinating agent resides.

coordinator subsection

The subsection of an application that starts other subsections (if any) and returns results to the application.

correlated columns

In SQL, a relationship between the value of one column and the value of another column.

correlated reference

A reference to a column of a table that is outside a subquery.

correlated subquery

A subquery that contains a correlated reference to a column of a table that is outside the subquery.

correlation ID

In DB2 UDB for OS/390, an identifier that is associated with a specific thread. In TSO, it is either an authorization ID or the job name.

correlation name

An identifier designating a table or view within a single SQL statement. It can be defined in any FROM clause or in the first clause of an UPDATE or DELETE statement.

cost category

A category into which DB2 UDB for OS/390 places cost estimates for SQL statements at the time the statement is bound. A cost estimate can be placed in either of the following cost categories:

A: Indicates that DB2 UDB for OS/390 had enough information to make a cost estimate without using default values.
B: Indicates that some condition exists for which DB2 UDB for OS/390 was forced to use default values for its estimate.

The cost category is externalized in the COST_CATEGORY column of DSN_STATEMNT_TABLE when a statement is explained.

country code

When accessing the database, the country code of the application is used to determine the date and time presentation (display and print) formats. It is also used with the code page to determine the default collating sequence for the database.

coupling facility

In an OS/390 environment, a special PR/SM^(TM) LPAR logical partition that runs the coupling facility control program and provides high-speed caching, list processing, and locking functions in a Parallel Sysplex.

CP

See control point.

CPC

See central processor complex.

CPI-C

See Common Programming Interface Communications.

CPI-C side information profile

In SNA, the profile that specifies the conversation characteristics to use when allocating a conversation with a remote transaction program. The profile is used by local transaction programs that communicate through CPI Communications. It specifies the partner LU name (the name of the connection profile that contains the remote LU name), the mode name, and the remote transaction program name.

CP name

Control point name. A network-qualified name of a control point that consists of a network ID qualifier that identifies the network to which the control point node belongs.

crash recovery

The process of recovering from an immediate failure.

CRC

See command recognition character.

CRCR

In DB2 UDB for OS/390, conditional restart control record. See conditional restart.

create link pack area (CLPA)

An option used during IPL to initialize the link pack pageable area.

cross-memory linkage

In an OS/390 environment, a method for invoking a program in a different address space. The invocation is synchronous with respect to the caller.

cross-system coupling facility (XCF)

A component of OS/390 that provides functions to support cooperation between authorized programs running within a Parallel Sysplex.

cross-system extended services (XES)

A set of OS/390 services that enable multiple instances of an application or subsystem, running on different systems in a Parallel Sysplex environment, to implement high-performance, high-availability data sharing by using a coupling facility.

CS

See cursor stability.

CSA

See common service area.

CT

See cursor table.

current data

In DB2 UDB for OS/390, data within a host structure that is current with (identical to) the data within the base table.

current function path

An ordered list of schema names used in the resolution of unqualified references to functions and data types. In dynamic SQL, the current function path is found in the CURRENT FUNCTION PATH special register. In static SQL, it is defined in the FUNCPATH option for PREP and BIND commands.

current status rebuild

In DB2 UDB for OS/390, the second phase of restart processing during which the status of the subsystem is reconstructed from information on the log.

current working directory

The default directory of a process from which all relative path names are resolved.

cursor

A named control structure used by an application program to point to a specific row within some ordered set of rows. The cursor is used to retrieve rows from a set.

cursor stability (CS)

An isolation level that locks any row accessed by a transaction of an application while the cursor is positioned on the row. The lock remains in effect until the next row is fetched or the transaction is terminated. If any data is changed in a row, the lock is held until the change is committed to the database.

cursor table (CT)

In DB2 UDB for OS/390, the copy of the skeleton cursor table that is used by an executing application process.

cycle

In DB2 UDB for OS/390, a set of tables that can be ordered so that each table is a descendent of the one before it, and the first table is a descendent of the last table. A self-referencing table is a cycle with a single member.

D

DARI

Database Application Remote Interface. Obsolete term for stored procedure.

data area

A memory area used by a program to hold information.

database access thread

In DB2 UDB for OS/390, a thread that accesses data at the local subsystem on behalf of a remote subsystem.

database administrator (DBA)

A person who is responsible for the design, development, operation, safeguarding, maintenance, and use of a database.

Database Application Remote Interface (DARI)

Obsolete term for stored procedure.

database catalog

In the Data Warehouse Center, a collection of tables that contains descriptions of database objects such as tables, views, and indexes.

database client

A workstation used to access a database that is on a database server.

database connection services (DCS) directory

A directory that contains entries for remote databases and the corresponding application requester used to access them.

database descriptor (DBD)

An internal representation of a DB2 UDB for OS/390 database definition, which reflects the data definition that is in the DB2 UDB for OS/390 catalog. The objects that are defined in a database descriptor are table spaces, tables, indexes, index spaces, and relationships.

database directory

A directory that contains database access information for all databases to which a client can connect.

database engine

The part of the database manager providing the base functions and configuration files needed to use the database.

database log

A set of primary and secondary log files consisting of log records that record all changes to a database. The database log is used to roll back changes for units of work that are not committed and to recover a database to a consistent state.

database-managed space (DMS) table space

A table space whose space is managed by the database. Contrast with system-managed space (SMS) table space.

database management system (DBMS)

Synonym for database manager.

database manager

A computer program that manages data by providing the services of centralized control, data independence, and complex physical structures for efficient access, integrity, recovery, concurrency control, privacy, and security.

database manager instance

A logical database manager environment similar to an image of the actual database manager environment. You can have several instances of the database manager product on the same workstation. You can use these instances to separate the development environment from the production environment, tune the database manager to a particular environment, and protect sensitive information from a particular group of people.

database node

See database partition.

database object

Anything that can be created or manipulated with SQL--for example, tables, views, indexes, packages, triggers, or table spaces.

database partition

A part of the database that consists of its own user data, indexes, configuration files, and transaction logs. Sometimes called a node or database node.

database request module (DBRM)

A data set member that is created by the DB2 UDB for OS/390 precompiler and that contains information about SQL statements. DBRMs are used in the bind process.

database server

A functional unit that provides database services for databases.

database system monitor

A collection of programming APIs that monitor performance and status information about the database manager, databases, and applications using the database manager and DB2 Connect.

data blocking

The process of specifying how many minutes worth of change data will be replicated during a subscription cycle. Contrast with blocking.

data currency

In DB2 UDB for OS/390, the state in which data that is retrieved into a host variable in your program is a copy of data in the base table.

data definition language (DDL)

A language for describing data and its relationships in a database. Synonym for data description language.

data definition name (ddname)

In DB2 UDB for OS/390, the name of a data definition (DD) statement that corresponds to a data control block that contains the same name.

data description language

Synonym for data definition language.

DataJoiner

A separately available product that provides client applications integrated access to distributed data and provides a single database image of a heterogeneous environment. With DataJoiner, a client application can join data (using a single SQL statement) that is distributed across multiple database management systems or update a single remote data source as if the data were local.

DataJoiner Replication Administration (DJRA) tool

A database administration tool that you can use to perform various replication administration tasks. Unlike the Control Center, the DJRA tool can be used to administer replication for non-IBM databases. Contrast with Control Center.

DATALINK

A DB2 data type that enables logical references from the database to a file stored outside the database.

data link control (DLC)

In SNA, the protocol layer that consists of the link stations that schedule data transfer over a link between two nodes and perform error control for the link.

data manipulation language (DML)

A subset of SQL statements used to manipulate data.

datamart

A subset of a data warehouse that contains data tailored for the specific needs of a department or team. A datamart can be a subset of a warehouse for your entire organization, such as data contained in OLAP tools.

data partition

In an OS/390 environment, a VSAM data set that is contained within a partitioned table space.

data sharing

The ability of two or more DB2 UDB for OS/390 subsystems to directly access and change a single set of data.

data sharing group

A collection of one or more DB2 UDB for OS/390 subsystems that directly access and change the same data while maintaining data integrity.

data sharing member

A DB2 UDB for OS/390 subsystem that is assigned by XCF services to a data sharing group.

data space

In DB2 UDB for OS/390, a range of up to 2 gigabytes of contiguous virtual storage addresses that a program can directly manipulate. Unlike an address space, a data space can hold only data; it does not contain common areas, system data, or programs.

data type

In SQL, an attribute of columns, literals, host variables, special registers, and the results of functions and expressions.

Data Warehouse Center

A graphical interface, and the software behind it, that enables you to work with the components of the warehouse. You can use the Data Warehouse Center to define and manage the warehouse data and the processes that create the data in the warehouse.

Data Warehouse Center administrative interface

The user interface to the administration functions of the Data Warehouse Center. The interface can be on the Data Warehouse Center server or on different machines for multiple administrators.

Data Warehouse Center program

A program, supplied with the Data Warehouse Center, that can be started from the Data Warehouse Center and that is automatically defined, for example, DB2 Load programs and transformers.

Data Warehouse Center property

An attibute that applies across sessions of the Data Warehouse Center, such as the warehouse control database that contains the technical metadata. See also property.

date

A three-part value that designates a day, month, and year.

date duration

A DECIMAL(8,0) value that represents a number of years, months, and days.

datetime value

A value of the data type DATE, TIME, or TIMESTAMP.

DBA

See database administrator.

DBA Utility

A tool that lets DB2 users configure databases and database manager instances, manage the directories necessary for accessing local and remote databases, back up and recover databases or table spaces, and manage media on a system using a graphical interface. The tasks provided by this tool can be accessed from the Control Center.

DBCLOB

See double-byte character large object.

DBCS

See double-byte character set.

DBD

See database descriptor.

DBID

Database identifier.

DBMS

Database management system. See database manager.

DBMS instance connection

A logical connection between an application and an agent process or thread owned by a DB2 instance.

DBRM

See database request module.

DB2 CLI

DB2 Call Level Interface. An alternative SQL interface for the DB2 family of products that takes full advantage of DB2 capability.

DB2 command

An instruction to the DB2 UDB for OS/390 subsystem allowing a user to start or stop DB2 UDB for OS/390, to display information on current users, to start or stop databases, to display information on the status of databases, and so on.

DB2 Connect

A product that provides the function necessary (DRDA application requester support) for client applications to read and update data stored in DRDA application servers.

DB2 extender

A program that you can use to store and retrieve data types beyond the traditional numeric and character data, such as image, audio, and video data, and complex documents.

DB2I

In DB2 UDB for OS/390, DATABASE 2 Interactive.

DB2I Kanji Feature

In DB2 UDB for OS/390, the tape that contains the panels and jobs that allow a site to display DB2I panels in Kanji.

DB2 PM

In DB2 UDB for OS/390, DATABASE 2 Performance Monitor.

DB2 SDK

See DB2 Application Development Client.

DB2 Application Development Client (DB2 SDK)

A collection of tools that help developers create database applications.

DB2 thread

The DB2 UDB for OS/390 structure that describes an application's connection, traces its progress, processes resource functions, and delimits its accessibility to DB2 UDB for OS/390 resources and services.

DB2UEXIT

An optional, user-written executable program that the database manager invokes to move or retrieve archive log files.

DCE

See Distributed Computing Environment.

DCE ticket

In an OS/390 environment, a transparent application mechanism that transmits the identity of an initiating principal to its target. A simple ticket contains the principal's identity, a session key, a timestamp, and other information, which is sealed using the target's secret key.

DCLGEN

See declarations generator.

DDF

See distributed data facility.

DDL

See data definition language.

ddname

See data definition name.

deadlock

A condition under which a transaction cannot proceed because it is dependent on exclusive resources that are locked by some other transaction, which in turn is dependent on exclusive resources in use by the original transaction.

deadlock detector

A process within the database manager that monitors the states of the locks to determine if a deadlock condition exists. When a deadlock condition is detected, the detector stops one of the transactions involved in the deadlock. This transaction is rolled back and the other transactions proceed.

declarations generator (DCLGEN)

A subcomponent of DB2 UDB for OS/390 that generates SQL table declarations and COBOL, C, or PL/I data structure declarations that conform to the table. The declarations are generated from DB2 UDB for OS/390 system catalog information. DCLGEN is also a DSN subcommand.

deferred embedded SQL

In DB2 UDB for OS/390, SQL statements that are neither fully static nor fully dynamic. Like static statements, they are embedded within an application, but like dynamic statements, they are prepared during the execution of the application.

definition metadata

In the Data Warehouse Center, information about the format of the data warehouse (the schema), the sources of the data, and the transformations applied in loading the data.

degree of parallelism

In DB2 UDB for OS/390, the number of concurrently executed operations that are initiated to process a query.

delete-connected

In SQL, a table that is a dependent of table P or a dependent of a table to which delete operations from table P cascade.

delete rule

A rule associated with a referential constraint that either restricts the deletion of a parent row or specifies the effect of such a deletion on the dependent rows.

delete trigger

In DB2 UDB for OS/390, a trigger that is defined with the triggering SQL operation DELETE.

delimited identifier

A sequence of characters enclosed within double quotation marks. The sequence must consist of a letter followed by zero or more characters, each of which is a letter, digit, or the underscore character.

delimiter

A character or flag that groups or separates items of data.

delimiter token

A string constant, a delimited identifier, an operator symbol, or any of the special characters shown in syntax diagrams.

dependent

In SQL, an object (row, table, or table space) that has at least one parent. See parent row, parent table, parent table space.

dependent logical unit (DLU)

A logical unit that requires assistance from a system services control point (SSCP) to instantiate an LU-to-LU session.

dependent row

A row that contains a foreign key that matches the value of a parent key in the parent row. The foreign key value represents a reference from the dependent row to the parent row.

dependent table

A table that is a dependent in at least one referential constraint.

descendent

An object that is a dependent of an object or is the dependent of a descendent of an object.

descendent row

A row that is dependent on another row or a row that is a descendent of a dependent row.

descendent table

A table that is a dependent of another table or a descendent of a dependent table.

deterministic function

See not-variant function.

device name

A name reserved by the system, or a device driver that refers to a specific device.

DFHSM

In an OS/390 environment, Data Facility Hierarchical Storage Manager.

DFP

In an OS/390 environment, Data Facility Product.

dictionary

A collection of language-related linguistic information that the Text Extender uses during text analysis, indexing, retrieval, and highlighting of documents in a particular language.

differential refresh

In DB2 replication, a process in which only changed data is copied to the target table, replacing existing data. Contrast with full refresh.

dimension

In the OLAP Starter Kit, a data category, such as time, accounts, products, or markets. Dimensions represent the highest consolidation level in a multidimensional database outline.

directed join

A relational operation in which all of the rows in one or both of the joined tables are rehashed and directed to new database partitions based on the join predicate. If all of the partitioning key columns in a table participate in the equijoin predicates, the other table is rehashed; otherwise (if there is at least one equijoin predicate), both tables are rehashed.

directory

The DB2 UDB for OS/390 system database that contains internal objects such as database descriptors and skeleton cursor tables.

directory services

A portion of the APPN protocols that maintains information about the location of resources in an APPN network.

disable

To restore a database, a text table, or a text column to its condition before it was enabled for the Text Extender by removing the items created during the enabling process.

distinct type

A user-defined data type that is internally represented as an existing type (its source type), but is considered to be a separate and incompatible type for semantic purposes.

Distributed Computing Environment (DCE)

A set of services and tools that support the creation, use, and maintenance of distributed applications in a heterogeneous computing environment. DCE is independent of the operating system and network; it provides interoperability and portability across heterogeneous platforms.

distributed data facility (DDF)

A set of DB2 UDB for OS/390 components through which DB2 UDB for OS/390 communicates with another RDBMS.

distributed directory database

The complete listing of all the resources in the network as maintained in the individual directories scattered throughout an APPN network. Each node has a piece of the complete directory, but it is not necessary for any one node to have the entire list. Entries are created, modified, and deleted through system definition, operator action, automatic registration, and ongoing network search procedures. Synonym for distributed network directory.

distributed network directory

See distributed directory database.

distributed relational database

A database whose tables are stored on different but interconnected computing systems.

Distributed Relational Database Architecture (DRDA)

The architecture that defines formats and protocols for providing transparent access to remote data. DRDA defines two types of functions, the application requester function and the application server function.

distributed request

In a federated database system, an SQL query directed to two or more data sources.

distributed unit of work (DUOW)

A unit of work that allows SQL statements to be submitted to multiple relational database management systems, but no more than one system per SQL statement.

DJRA tool

A database administration tool that you can use to perform various replication administration tasks. Unlike the Control Center, the DJRA tool can also be used to administer replication for non-IBM databases. Contrast with Control Center.

DLC

See data link control.

DLU

See dependent logical unit.

DML

See data manipulation language.

DMS table space

See database-managed space table space.

DNS

See domain name system.

Document Access Definition (DAD)

A definition that is used to enable an XML Extender column of an XML collection, which is XML formatted.

document model

The definition of the structure of a document in terms of the sections that it contains. The Text Extender uses a document model when indexing.

domain name

The name by which TCP/IP applications refer to a TCP/IP host within a TCP/IP network. A domain name consists of a sequence of names separated by dots.

domain name server (DNS)

A TCP/IP network server that manages a distributed directory that is used to map TCP/IP host names to IP addresses.

domain name system

The distributed database system used by TCP/IP to map human-readable machine names into IP addresses.

Domino Go Web server

The Web server offered by Lotus Corp. and IBM, that offers both regular and secure connections. ICAPI and GWAPI are the interfaces provided with this server.

double-byte character large object (DBCLOB)

A sequence of double-byte characters, where the size can be up to 2 gigabytes. A data type that can be used to store large double-byte text objects. Also called double-byte character large object string. Such a string always has an associated code page.

double-byte character set (DBCS)

A set of characters in which each character is represented by two bytes.

double-precision floating point number

In SQL, a 64-bit approximate representation of a real number.

drain

In DB2 UDB for OS/390, the act of acquiring a locked resource by quiescing access to that object.

drain lock

In DB2 UDB for OS/390, a lock on a claim class that prevents a claim from occurring.

DRDA

See Distributed Relational Database Architecture.

DRDA access

In DB2 UDB for OS/390, a method of accessing distributed data by which you can connect to another location, using an SQL statement, to execute packages that were previously bound at that location. The SQL CONNECT or three-part name statement is used to identify application servers, and SQL statements are executed using packages that were previously bound at those servers. Contrast with private protocol access.

DSN

(1) The default subsystem name for DB2 UDB for OS/390.

(2) The name of the TSO command processor of DB2 UDB for OS/390.

(3) The first three characters of the names of DB2 UDB for OS/390 modules and macros.

DUOW

See distributed unit of work.

duration

In SQL, a number that represents an interval of time. See date duration, labeled duration, and time duration.

dynamic bind

A process by which SQL statements are bound as they are entered. See also bind.

dynamic SQL

SQL statements that are prepared and run within a running program. In dynamic SQL, the SQL source is contained in host language variables rather than being coded into the program. The SQL statement might change several times while the program is running.

E

EA-enabled table space

In DB2 UDB for OS/390, a table space or index space that is enabled for extended addressability and that contains individual partitions (or pieces, for LOB table spaces) that are greater than 4 GB.

EBCDIC

Extended binary-coded decimal interchange code. A coded character set of 256 8-bit characters.

EDM pool

In DB2 UDB for OS/390, a pool of main storage that is used for database descriptors, application plans, authorization cache, application packages, and dynamic statement caching.

EID

Event identifier.

embedded SQL

SQL statements coded within an application program. See static SQL.

EN

See end node.

enable

To prepare a database, a text table, or a text column for use by the Text Extender.

enclave

In Language Environment (which is used by DB2 UDB for OS/390), an independent collection of routines, one of which is designated as the main routine. An enclave is similar to a program or run unit.

encoding scheme

A set of rules to represent character data.

end node (EN)

In APPN, a node that supports sessions between its local control point and the control point in an adjacent network node.

enhanced conflict detection

Conflict detection that guarantees data integrity among all replicas and the source table. The Apply program locks all replicas or user tables in the subscription set against further transactions. It begins detection after all changes made prior to locking have been captured. See also conflict detection, standard conflict detection, and row-replica conflict detection.

environment handle

A handle that identifies the global context for database access. All data that is pertinent to all objects in the environment is associated with this handle.

environment profile

A script that is provided with the Text Extender that contains settings for environment variables.

EOM

End of memory.

EOT

End of task.

equijoin

A join in which the predicate contains an equals operator, for example, T1.C1 = T2.C2.

error page range

A range of pages that are considered to be physically damaged. DB2 UDB for OS/390 does not allow users to access any pages that fall within this range.

escape character

The symbol that is used to enclose an SQL delimited identifier. The escape character is the double quotation mark, except in COBOL applications, where the user assigns the symbol, which is either a double quotation mark or an apostrophe.

ESDS

In an OS/390 environment, entry sequenced data set.

ESMT

In the OS/390 environment, the external subsystem module table of IMS.

EUC

See Extended UNIX Code.

event monitor

A database object for monitoring and collecting data on database activities over a period of time.

event timing

In DB2 replication, the most precise method of controlling when to start a subscription cycle. It requires that you specify an event and the time when you want the event processed. Contrast with interval timing and on-demand timing.

exception table

In DB2 UDB for OS/390, a table that holds rows that violate referential constraints or table check constraints that the CHECK DATA utility finds.

exclusive lock

A lock that prevents concurrently executing application processes from accessing database data.

executable statement

An SQL statement that can be embedded in an application program, dynamically prepared and executed, or issued interactively.

exit routine

A program that receives control from another program (such as DB2 UDB for OS/390) to perform specific functions.

explain

To capture detailed information about the access plan that was chosen by the SQL compiler to resolve an SQL statement. The information describes the decision criteria used to choose the access plan.

explainable statement

An SQL statement for which the explain operation can be performed. Explainable statements are SELECT, UPDATE, INSERT, DELETE, and VALUES.

explained statement

An SQL statement for which an explain operation was performed.

explained statistics

Statistics for a database object that was referenced in an SQL statement at the time that the statement was explained.

explain snapshot

A capture of the current internal representation of an SQL query and related information. This information is required by the Visual Explain tool.

explicit hierarchical locking

In DB2 UDB for OS/390, locking that is used to make the parent-child relationship between resources known to IRLM. This kind of locking avoids global locking overhead when no inter-DB2 interest exists on a resource.

explicit privilege

A privilege that has a name and is held as the result of SQL GRANT and REVOKE statements, for example, the SELECT privilege. Contrast with implicit privilege.

export

To copy data from database manager tables to a file using formats such as PC/IXF, DEL, WSF, or ASC. Contrast with import.

exposed name

A correlation name, a table, or a view name specified in a FROM clause for which a correlation name is not specified.

expression

An SQL operand or a collection of operators and operands that yields a single value.

extended recovery facility (XRF)

In an OS/390 environment, a facility that minimizes the effect of failures in MVS, VTAM, the host processor, or high-availability applications during sessions between high-availability applications and designated terminals. This facility provides an alternative subsystem to take over sessions from the failing subsystem.

Extended UNIX Code (EUC)

A protocol that can support sets of characters from 1 to 4 bytes in length. EUC is a means of specifying a collection of code pages rather than actually being a code page encoding scheme itself. This is the UNIX alternative to the PC double-byte (DBCS) code page encoding schemes.

extent

An allocation of space, within a container of a table space, to a single database object. This allocation consists of multiple pages.

extent map

A metadata structure stored within a table space that records the allocation of extents to each object in the table space.

external CCD table

In DB2 replication, a CCD table that can be subscribed to directly because it is a registered replication source. It has its own row in the register table, where it is referenced as SOURCE_OWNER and SOURCE_TABLE. Contrast with internal CCD table.

external function

In DB2 UDB for OS/390, a function for which the body is written in a programming language that takes scalar argument values and produces a scalar result for each invocation. Contrast with sourced function and built-in function.

external routine

In DB2 UDB for OS/390, a user-defined function or stored procedure that is based on code that is written in an external programming language.

F

fact table

In the OLAP Starter Kit, a table, or in many cases a set of four tables, in DB2 that contains all data values for a relational cube.

failed member state

In DB2 UDB for OS/390, a state of a member of a data sharing group. When a member fails, the XCF permanently records the failed member state. This state usually means that the member's task, address space, or MVS system terminated before the state changed from active to quiesced.

fallback

The process of returning to a previous release of DB2 UDB for OS/390 after attempting or completing migration to a current release.

false global lock contention

In DB2 UDB for OS/390, an indication of contention from the coupling facility when multiple lock names are hashed to the same indicator and when no real contention exists.

fast communication manager (FCM)

A group of functions that provide internodal communication support.

federated database system

(1) A DB2 server and multiple data sources that the server sends queries to. In a federated database system, a client application can join data that is distributed across multiple database management systems using a single SQL statement and view the data as if it were local.

(2) A distributed computing system that consists of:

A DB2 server, called a federated server.
Multiple data sources to which the federated server sends queries.
Each data source consists of an instance of a relational database management system plus the database or databases that the instance supports.
The data sources are semi-autonomous. For example, the federated server can send queries to Oracle data sources at the same time that Oracle applications are accessing these data sources.

fenced

Pertaining to a type of user-defined function or stored procedure that is defined to protect the DBMS from modifications by the function. The DBMS is isolated from the function or stored procedure by a barrier. Contrast with not-fenced.

field procedure

In DB2 UDB for OS/390, a user-written exit routine that is designed to receive a single value and transform (encode or decode) it in any way that the user can specify.

file reference variable

A host variable that is used to indicate that data resides in a file on the client rather than in a client memory buffer.

file server

A workstation that runs the NetWare operating system software and acts as a network server. DB2 uses the file server to store DB2 server address information, which a DB2 client retrieves to establish an IPX/SPX client-server connection.

filter factor

In DB2 UDB for OS/390, a number between zero and one that estimates the proportion of rows in a table for which a predicate is true.

first failure service log

A file (db2diag.log) that contains diagnostic messages, diagnostic data, alert information, and related dump information. This file is used by database administrators.

fixed-length string

A character or graphic string whose length is specified and cannot be changed. Contrast with varying-length string.

flagger

A precompiler option that identifies SQL statements in applications that do not conform to selected validation criteria (for example, the ISO/ANSI SQL92 entry-level standard).

flat file interface

A set of Net.Data built-in functions that let you read and write data from plain-text files.

foreign update

An update that was applied to a target table and replicated to the local table.

forward log recovery

The third phase of restart processing during which DB2 UDB for OS/390 processes the log in a forward direction to apply all REDO log records.

forward recovery

A process used to roll forward a database or table space. It allows a restored database or table space to be rebuilt to a specified point in time by applying the changes recorded in the database log.

free space

In DB2 UDB for OS/390, the total amount of unused space in a page. The space that is not used to store records or control information is free space.

full outer join

The result of an SQL join operation that includes the matched rows of both tables that are being joined and preserves the unmatched rows of both tables. See join.

full refresh

In DB2 replication, a process in which all of the data of interest in a user table is copied to the target table, replacing existing data. Contrast with differential refresh.

fullselect

A subselect, a values-clause, or a number of both that are combined by set operators.

fully qualified LU name

See network-qualified name.

function

(1) A mapping, embodied as a program (the function body), that can be invoked by using zero or more input values (arguments) to a single value (the result).

(2) In DB2 UDB for OS/390, a specific purpose of an entity or its characteristic action such as a column function or scalar function. Functions can be user-defined, built-in, or generated by DB2 UDB for OS/390.

function body

The piece of code that implements a function.

function definer

In DB2 UDB for OS/390, the authorization ID of the owner of the schema of the function that is specified in the CREATE FUNCTION statement.

function family

A set of functions with the same function name. The context determines whether the usage refers to a set of functions within a particular schema, or all the relevant functions with the same name within the current function path.

function implementer

In DB2 UDB for OS/390, the authorization ID of the owner of the function program and function package.

function invocation

The use of a function together with any argument values being passed to the function body. The function is invoked by its name.

function package

In DB2 UDB for OS/390, a package that results from binding the DBRM for a function program.

function package owner

In DB2 UDB for OS/390, the authorization ID of the user who binds the function program's DBRM into a function package.

function path

An ordered list of schema names that restricts the search scope for unqualified function invocations and provides a final arbiter for the function selection process.

function path family

All the functions of the given name in all the schemas identified (or used by default) in the user's function path.

function resolution

The process, internal to the DBMS, for which a particular function instance is selected for invocation. The function name, the data types of the arguments, and the function path are used to make the selection. Synonym for function selection.

function selection

See function resolution.

function shipping

The shipping of the subsections of a request to the specific node that contains the applicable data.

function signature

The logical concatenation of a fully qualified function name with the data types of all of its parameters. Each function in a schema must have a unique signature.

function template

In a federated database, a partial function that has no executable code. The user maps it to a data source function, so that the data source function can be invoked from the federated server.

G

gap

In DB2 replication, a situation in which the Capture program is not able to read a range of log or journal records, so there is potential loss of change data.

GBP

Group buffer pool.

GBP-dependent

In DB2 UDB for OS/390, the status of a page set or page set partition that is dependent on the group buffer pool. Either read/write interest is active among DB2 subsystems for this page set, or the page set has changed pages in the group buffer pool that are not yet cast out to DASD.

generalized trace facility (GTF)

In an OS/390 environment, a service program that records significant system events such as I/O interrupts, SVC interrupts, program interrupts, or external interrupts.

generic resource name

In an OS/390 environment, a name that VTAM uses to represent several application programs that provide the same function in order to handle session distribution and balancing in a Parallel Sysplex environment.

getpage

An operation in which DB2 UDB for OS/390 accesses a data page.

GIMSMP

In an OS/390 environment, the load module name for the System Modification Program/Extended, a basic tool for installing, changing, and controlling changes to programming systems.

global lock

In DB2 UDB for OS/390, a lock that provides concurrency control within and among DB2 subsystems. The scope of the lock is across all DB2 subsystems of a data sharing group.

global lock contention

Conflicts on locking requests between different DB2 UDB for OS/390 members of a data sharing group when those members are trying to serialize shared resources.

global table lock

A table lock that is acquired on all nodes in a table's nodegroup.

global transaction

A unit of work in a distributed transaction processing environment in which multiple resource managers are required.

governor

See resource limit facility.

grant

To give a privilege or authority to an authorization ID.

graphic character

A DBCS character.

graphic string

A sequence of DBCS characters.

gross lock

In DB2 UDB for OS/390, the shared, update, or exclusive mode locks on a table, partition, or table space.

group

(1) A logical organization of users that have IDs according to activity or resource access authority.

(2) In Satellite Edition, a collection of satellites that share characteristics such as database configuration and the application that runs on the satellite.

group buffer pool duplexing

In an OS/390 environment, the ability to write data to two instances of a group buffer pool structure: a primary group buffer pool and a secondary group buffer pool. OS/390 publications refer to these instances as the "old" (for primary) and "new" (for secondary) structures.

group name

In an OS/390 environment, the XCF identifier for a data sharing group.

group restart

In an OS/390 environment, a restart of at least one member of a data sharing group after the loss of either locks or the shared communications area.

group scope

See command scope.

GTF

See generalized trace facility.

GWAPI

Domino Go Web server API.

H

handle

(1) A variable that represents an internal structure within a software system.

(2) A character string that is created by an extender that is used to represent an image, audio, or video object in a table. A handle is stored for an object in a user table and in administrative support tables. In this way, an extender can link the handle that is stored in a user table with information about the object that is stored in the administrative support tables.

(3) A binary value that identifies a text document. A handle is created for each text document in a text column when that column is enabled for use by the Text Extender.

hash partitioning

A partitioning strategy in which a hash function is applied to the partitioning key value to determine the database partition to which the row is assigned.

hiperspace

In an OS/390 environment, a range of up to 2 GB of contiguous virtual storage addresses that a program can use as a buffer. Like a data space, a hiperspace can hold user data; it does not contain common areas or system data. Unlike an address space or a data space, data in a hiperspace is not directly addressable. To manipulate data in a hiperspace, you bring the data into the address space in 4-KB blocks.

home address space

In an OS/390 environment, the area of storage that OS/390 currently recognizes as dispatched.

hop

In APPN, a portion of a route that has no intermediate nodes. A hop consists of a single transmission group connecting adjacent nodes.

host

In TCP/IP, any system that has at least one Internet address associated with it.

host computer

(1) In a computer network, a computer that provides services such as computation, database access, and network control functions.

(2) The primary or controlling computer in a multiple computer installation.

host identifier

A name declared in the host program.

host language

Any programming language in which you can embed SQL statements.

host node

In SNA, a subarea node that contains a system services control point (SSCP), for example, an IBM System/390 computer with MVS and VTAM.

host program

A program written in a host language that contains embedded SQL statements.

host structure

In an application program, a structure that is referred to by embedded SQL statements.

host variable

In an application host program, a variable that is referred to by embedded SQL statements. Host variables are programming variables in the application program and are the primary mechanism for transmitting data between tables in the database and application program work areas.

HSM

In an OS/390 environment, hierarchical storage manager.

I

ICAPI

Internet Connection API.

ICF

In an OS/390 environment, integrated catalog facility.

IDCAMS

In an OS/390 environment, an IBM program that is used to process access method services commands. It can be invoked as a job or jobstep, from a TSO terminal or from within a user's application program.

IDCAMS LISTCAT

In an OS/390 environment, a facility for obtaining information that is contained in the access method services catalog.

identify

A request that an attachment service program (in an address space that is separate from DB2 UDB for OS/390) issues through the MVS subsystem interface to inform DB2 UDB for OS/390 of its existence and to initiate the process of becoming connected to DB2.

IFCID

In DB2 UDB for OS/390, instrumentation facility component identifier.

IFI

In DB2 UDB for OS/390, instrumentation facility interface.

IFI call

In DB2 UDB for OS/390, an invocation of the instrumentation facility interface (IFI) by means of one of its defined functions.

IFP

In an OS/390 environment, IMS Fast Path.

ILU

See independent logical unit.

image copy

An exact reproduction of all or part of a table space. DB2 UDB for OS/390 provides utility programs to make full image copies (to copy the entire table space) or incremental image copies (to copy only those pages that were modified since the last image copy).

implicit privilege

A privilege that accompanies the ownership of an object, such as the privilege to drop a synonym one owns or the holding of an authority, such as the privilege of SYSADM authority to terminate any utility job.

import

To copy data from an external file, using formats such as PC/IXF, DEL, WSF or ASC, into database manager tables. Contrast with export.

import metadata

The process of bringing metadata into the Data Warehouse Center, either dynamically (from the user interface) or in batch.

import utility

Transactional utility that inserts user-supplied record data into a table. Contrast with load utility.

IMS

Information Management System.

IMS attachment facility

A DB2 UDB for OS/390 subcomponent that uses OS/390 subsystem interface (SSI) protocols and cross-memory linkage to process requests from IMS to DB2 UDB for OS/390 and to coordinate resource commitment.

IMS DB

Information Management System Database.

IMS TM

Information Management System Transaction Manager.

in-abort

A status of a unit of recovery. If DB2 UDB for OS/390 fails after a unit of recovery begins to be rolled back, but before the process is completed, DB2 UDB for OS/390 continues to back out the changes during restart.

in-commit

A status of a unit of recovery. If DB2 UDB for OS/390 fails after beginning its two-phase commit processing, it "knows," when restarted, that changes made to data are consistent.

incremental bind

A process by which SQL statements are bound during the execution of an application process, because they could not be bound during the bind process, and VALIDATE(RUN) was specified. See also bind.

independent

In DB2 UDB for OS/390, an object (row, table, or table space) that is neither a parent nor a dependent of another object.

independent logical unit (ILU)

A logical unit that is able to activate an LU-to-LU session without assistance from a system services control point (SSCP). An ILU does not have an SSCP-to-LU session. Contrast with dependent logical unit.

index

A set of pointers that are logically ordered by the values of a key. Indexes provide quick access to data and can enforce uniqueness on the rows in the table.

index file

A file that contains indexing information used by the Video Extender to find a shot or an individual frame in a video clip.

index key

The set of columns in a table used to determine the order of index entries.

index partition

The part of an index that is associated with a table partition at a given node. An index defined on a table is implemented by multiple index partitions, one per table partition.

index sargable predicates

SQL predicates that are applied to index entries in index leaf pages to reduce the number of index entries that qualify the SQL request. They help reduce the number of data rows accessed.

index space

In DB2 UDB for OS/390, a page set that is used to store the entries of one index.

index specification

In a federated database system, a set of metadata that pertains to a data source table. This metadata is made up of information that an index definition typically contains, for example, which column or columns to search in order to retrieve information quickly. The user might supply the federated server with this metadata if the table has no index or if it has an index that is unknown to the federated server. The purpose of the metadata is to facilitate retrieval of the table's data.

indicator column

In DB2 UDB for OS/390, a 4-byte value that is stored in a base table in place of an LOB column.

indicator variable

A variable used to represent the null value in an application program. If the value for the selected column is null, a negative value is placed in the indicator variable.

indoubt

A status of a unit of recovery. If DB2 UDB for OS/390 fails after it finishes its phase 1 commit processing and before it starts phase 2, only the commit coordinator knows if an individual unit of recovery is to be committed or rolled back. At emergency restart, if DB2 UDB for OS/390 lacks the information that it needs to make this decision, the status of the unit of recovery is indoubt until DB2 UDB for OS/390 obtains this information from the coordinator. More than one unit of recovery can be indoubt at restart.

indoubt resolution

In DB2 UDB for OS/390, the process of resolving the status of an indoubt logical unit of work to either the committed or the rollback state.

indoubt transaction

A transaction in which one phase of a two-phase commit completes successfully but the system fails before a subsequent phase can complete.

inflight

A status of a unit of recovery. If DB2 UDB for OS/390 fails before its unit of recovery completes phase 1 of the commit process, it merely backs out the updates of its unit of recovery at restart. These units of recovery are termed inflight.

information catalog

The database, managed by the Information Catalog Manager, that contains descriptive data (business metadata) that helps users identify and locate data and information that is available to them in the organization. The information catalog also contains some technical metadata.

Information Catalog Manager

An application for organizing, maintaining, finding, and using business information.

inheritance

The passing of class resources or attributes from a parent class downstream in the class hierarchy to a child class.

initialization fullselect

The first fullselect in a recursive common table expression that gets the direct children of the initial value from the source table.

inner join

A join method in which a column that is not common to all of the tables being joined is dropped from the resultant table. Contrast with outer join.

inoperative package

A package that cannot be used because a function that it depends on has been dropped. Such a package must be explicitly rebound. Contrast with invalid package.

inoperative trigger

A trigger that depends on an object that has been dropped or made inoperative or on a privilege that has been revoked.

inoperative view

A view that is no longer usable because one of the following situations occurs:

SELECT privilege on a table or view that the view is dependent on is revoked from the definer of the view.
An object on which the view definition is dependent was dropped (or possibly made inoperative in the case of another view).

insert rule

A condition enforced by the database manager that must be met before a row can be inserted into a table.

insert trigger

In DB2 UDB for OS/390, a trigger that is defined with the triggering SQL operation INSERT.

install

The process of preparing a DB2 UDB for OS/390 subsystem to operate as an OS/390 subsystem.

installation verification scenario

A sequence of operations that exercises the main DB2 UDB for OS/390 functions and tests whether DB2 UDB for OS/390 was correctly installed.

instance

(1) See database manager instance.

(2) A logical DB2 extender server environment. You can have several instances of DB2 extenders server on the same workstation, but only one instance for each DB2 instance.

instrumentation facility component identifier (IFCID)

In DB2 UDB for OS/390, a value that names and identifies a trace record of an event that can be traced. As a parameter on the START TRACE and MODIFY TRACE commands, it specifies that the corresponding event is to be traced.

instrumentation facility interface (IFI)

A programming interface that enables programs to obtain online trace data about DB2 UDB for OS/390, to submit DB2 UDB for OS/390 commands, and to pass data to DB2 UDB for OS/390.

Interactive System Productivity Facility (ISPF)

In an OS/390 environment, an IBM licensed program that provides interactive dialog services.

inter-DB2 R/W interest

In DB2 UDB for OS/390, a property of data in a table space, index, or partition that has been opened by more than one member of a data sharing group and that has been opened for writing by at least one of those members.

intermediate network node

In APPN, a node that is part of a route between an origin logical unit (OLU) and a destination logical unit (DLU) but that neither contains the OLU or the DLU nor serves as the network server for either the OLU or DLU.

internal CCD table

A CCD table that cannot be subscribed to directly. It does not have its own row in the register table; it is referenced as CCD_OWNER and CCD_TABLE in the row for the associated replication source. Contrast with external CCD table.

internal resource lock manager (IRLM)

In an OS/390 environment, a subsystem that DB2 UDB for OS/390 uses to control communication and database locking.

Internet Protocol (IP)

A protocol used to route data from its source to its destination in an Internet environment.

Internetwork Packet Exchange (IPX)

A connectionless datagram protocol, used in a NetWare LAN environment, to transfer data to a remote node. IPX makes a best-effort attempt to send data packets, but does not guarantee reliable delivery of the data.

inter-partition parallelism

The ability to perform multiple database operations (such as index creation, database load, and SQL queries) at the same time across multiple partitions of a partitioned database. Contrast with intra-partition parallelism.

Inter-Process Communication (IPC)

A mechanism of an operating system that allows processes to communicate with each other.

interval timing

In DB2 replication, the simplest method of controlling when to start a subscription cycle. You must specify a date and a time for a subscription cycle to start, and set a time interval that describes how frequently you want the subscription cycle to run. Contrast with event timing and on-demand timing.

intra-partition parallelism

The ability to perform multiple database operations (such as index creation, database load, SQL queries) at the same time within a single database partition. Contrast with inter-partition parallelism.

intra-query parallelism;

The ability to process parts of a single query at the same time using either intra-partition parallelism, inter-partition parallelism, or both.

invalid package

A package that becomes invalid when an object that the package depends on is dropped. (The object is of a type other than function, for example, index.) Such a package is implicitly rebound upon invocation. Contrast with inoperative package.

invariant character set

In DB2 UDB for OS/390, (1) a character set, such as the syntactic character set, whose code point assignments do not change from code page to code page; (2) a minimum set of characters that is available as part of all character sets.

I/O parallelism

See parallel I/O.

IP

See Internet Protocol.

IP address

A 4-byte value that uniquely identifies a TCP/IP host.

IPX

Internetwork Packet Exchange.

IRLM

In DB2 UDB for OS/390, internal resource lock manager.

ISAPI

Microsoft Internet Server API.

isolation level

An attribute that defines the degree to which an application process is isolated from other concurrently executing application processes.

ISPF

In an OS/390 environment, Interactive System Productivity Facility.

ISPF/PDF

In an OS/390 environment, Interactive System Productivity Facility/Program Development Facility.

J

JCL

See job control language.

JES

See Job Entry Subsystem.

job control language (JCL)

A control language that is used to identify a job to an operating system and to describe the job's requirements.

Job Entry Subsystem (JES)

An IBM licensed program that receives jobs into the system and processes all output data that is produced by jobs.

job scheduler

A program used to automate certain tasks for running and managing database jobs.

join

An SQL relational operation that allows retrieval of data from two or more tables based on matching column values.

K

key

A column or an ordered collection of columns that are identified in the description of a table, index, or referential constraint.

key-sequenced data set (KSDS)

In an OS/390 environment, a VSAM file or data set whose records are loaded in key sequence and controlled by an index.

key-value based partitioning strategy

A strategy for assigning rows in a table to database partitions. Rows are assigned based on the values of the partitioning key columns.

keyword

(1) One of the predefined words of a computer, command language, or an application.

(2) A name that identifies an option used in an SQL statement.

KSDS

See key-sequenced data set.

L

labeled duration

A number that represents a duration of years, months, days, hours, minutes, seconds, or microseconds.

Language Environment

A module that provides access from a Net.Data macro to an external data source, such as DB2, or to a programming language, such as Perl.

large object (LOB)

A sequence of bytes with a length of up to 2 gigabytes. It can be any of three types: BLOB (binary), CLOB (single-byte character or mixed) or DBCLOB (double-byte character).

latch

A DB2 UDB for OS/390 internal mechanism for controlling concurrent events or the use of system resources.

LCID

In an OS/390 environment, log control interval definition.

LDS

See linear data set.

leaf page

In DB2 UDB for OS/390, a page that contains pairs of keys and RIDs and that points to actual data. Contrast with nonleaf page.

left outer join

In DB2 UDB for OS/390, the result of a join operation that includes the matched rows of both tables that are being joined and that preserves the unmatched rows of the first table. See join and right outer join.

length attribute

A value associated with a string that represents the declared fixed length or maximum length of the string.

LEN node

See low-entry networking node.

linear data set (LDS)

In an OS/390 environment, a VSAM data set that contains data but no control information. A linear data set can be accessed as a byte-addressable string in virtual storage.

linkage editor

A computer program for creating load modules from one or more object modules or load modules by resolving cross-references among the modules and, if necessary, adjusting addresses.

link-edit

In DB2 UDB for OS/390, the action of creating a loadable computer program using a linkage editor.

list prefetch

An access method that takes advantage of prefetching even in queries that do not access data sequentially. This is done by scanning the index and collecting RIDs in advance of accessing any data pages. These RIDs are then sorted, and data is prefetched using this list.

list structure

In an OS/390 environment, a coupling facility structure that lets data be shared and manipulated as elements of a queue.

Live Connection

A Net.Data component that consists of a Connection Manager and multiple cliettes. Live Connection manages the reuse of database and Java virtual machine connections.

L-lock

See logical lock.

load copy

A backup image of data that was loaded at a previous time and can be restored during roll-forward recovery.

load module

A program unit that is suitable for loading into main storage for execution. The output of a linkage editor.

load utility

A nontransactional utility that performs block updates of table data. Contrast with import utility.

LOB

See large object.

LOB locator

A mechanism that allows an application program to manipulate a large object (LOB) value in the database system. An LOB locator is a simple token value that represents a single LOB value. An application program retrieves an LOB locator into a host variable and can then apply SQL functions to the associated LOB value using the locator.

LOB lock

In DB2 UDB for OS/390, a lock on an LOB value.

LOB table space

In DB2 UDB for OS/390, a table space that contains all the data for a particular LOB column in the related base table.

local

A way of referring to any object that the local subsystem maintains. In DB2 UDB for OS/390, for example, a local table is a table that is maintained by the local DB2 subsystem. Contrast with remote.

local database

A database that is physically located on the workstation in use. Contrast with remote database.

local database directory

A directory where a database physically resides. Databases that are displayed in the local database directory are located on the same node as the system database directory.

locale

In DB2 UDB for OS/390, the definition of a subset of a user's environment that combines characters that are defined for a specific language and country, and a CCSID.

local lock

A lock that provides intra-DB2 concurrency control, but not inter-DB2 concurrency control; its scope is a single DB2 UDB for OS/390 system.

local subsystem

The unique RDBMS to which the user or application program is directly connected (in the case of DB2 UDB for OS/390, by one of the DB2 UDB for OS/390 attachment facilities).

local table lock

A table lock that is acquired only on a single database partition.

local update

An update to the base table, not to the replica.

location name

The name by which DB2 UDB for OS/390 refers to a particular DB2 subsystem in a network of subsystems. Contrast with LU name.

location path

A subset of the abbreviated syntax of the location path defined by XPath. A sequence of XML tags to identify an XML element or attribute. It is used in extracting user-defined functions to identify the subject to be extracted, and it is used in the Text Extender's search user-defined functions to identify the search criteria.

locator

See LOB locator.

lock

(1) A means of serializing events or access to data.

(2) A means of preventing uncommitted changes made by one application process from being perceived by another application process and for preventing one application process from updating data that is being accessed by another process.

(3) A means of controlling concurrent events or access to data. DB2 UDB for OS/390 locking is performed by the IRLM.

lock duration

The interval over which a DB2 UDB for OS/390 lock is held.

lock escalation

In the database manager, the response that occurs when the number of locks issued for one agent exceeds the limit specified in the database configuration; the limit is defined by the MAXLOCKS configuration parameter. During a lock escalation, locks are freed by converting locks on rows of a table into one lock on a table. This is repeated until the limit is no longer exceeded.

locking

The mechanism used by the database manager to ensure the integrity of data. Locking prevents concurrent users from accessing inconsistent data.

lock mode

A representation for the type of access that concurrently running programs can have to a resource that a DB2 UDB for OS/390 lock is holding.

lock object

The resource that is controlled by a DB2 UDB for OS/390 lock.

lock parent

For explicit hierarchical locking in DB2 UDB for OS/390, a lock that is held on a resource that has child locks that are lower in the hierarchy; usually, the table space or partition intent locks are the parent locks.

lock promotion

The process of changing the size or mode of a DB2 UDB for OS/390 lock to a higher level.

lock size

The amount of data controlled by a DB2 UDB for OS/390 lock on table data; the value can be a row, a page, an LOB, a partition, a table, or a table space.

lock structure

In DB2 UDB for OS/390, a coupling facility data structure that is composed of a series of lock entries to support shared and exclusive locking for logical resources.

log

(1) A file used to record changes made in a system.

(2) A collection of records that describe the events that occur during DB2 UDB for OS/390 execution and that indicate their sequence. The information thus recorded is used for recovery in the event of a failure during DB2 UDB for OS/390 execution.

(3) See database log.

log head

The oldest written log record in the active log.

logical claim

In DB2 UDB for OS/390, a claim on a logical partition of a nonpartitioning index.

logical drain

In DB2 UDB for OS/390, a drain on a logical partition of a nonpartitioning index.

logical index partition

In DB2 UDB for OS/390, the set of all keys that reference the same data partition.

logical lock (L-lock)

In DB2 UDB for OS/390, the lock type that transactions use to control intra-DB2 and inter-DB2 data concurrency between transactions. Contrast with physical lock.

logical node

A node on a processor that has more than one node assigned to it. See also node.

logical operator

A keyword that specifies how multiple search conditions are to be evaluated (AND, OR) or if the logical sense of a search condition is to be inverted (NOT).

logical page list (LPL)

In DB2 UDB for OS/390, a list of pages that are in error and that cannot be referenced by applications until the pages are recovered. The page is in logical error, because the actual media (coupling facility or DASD) might not contain any errors. Usually a connection to the media has been lost.

logical partition

In DB2 UDB for OS/390, a set of key or RID pairs in a nonpartitioning index that are associated with a particular partition.

logical recovery pending (LRECP)

In DB2 UDB for OS/390, the state in which the data and the index keys that refer to the data are inconsistent.

logical unit (LU)

(1) In SNA, a port through which an end user accesses the SNA network to communicate with another end user. An LU is capable of supporting many sessions with other LUs.

(2) In an OS/390 environment, an access point through which an application program accesses the SNA network in order to communicate with another application program. See also LU name.

logical unit 6.2 (LU 6.2)

The LU type that supports sessions between two applications using APPC.

logical unit of work (LUW)

The processing that a program performs between synchronization points.

logical unit of work identifier (LUWID)

In an OS/390 environment, a name that uniquely identifies a thread within a network. This name consists of a fully-qualified LU network name, an LUW instance number, and an LUW sequence number.

log initialization

The first phase of restart processing during which DB2 UDB for OS/390 attempts to locate the current end of the log.

log partition

The log file on each database partition that records database activity for that database partition.

log record

A record of an update to a database performed during a unit of work. This record is written after the log tail of the active log.

log record sequence number (LRSN)

A number that DB2 UDB for OS/390 generates and associates with each log record. The LRSN is also used for page versioning. The LRSNs that a particular DB2 UDB for OS/390 data sharing group generates form a strictly increasing sequence for each DB2 log and a strictly increasing sequence for each page across the data sharing group.

log table

A table created by the Text Extender that contains information about which text documents are to be indexed.

log tail

The log record that was written most recently in an active log.

log truncation

In DB2 UDB for OS/390, a process by which an explicit starting RBA is established. This RBA is the point at which the next byte of log data is to be written.

long string

(1) A varying-length string whose maximum length is greater than 254 bytes.

(2) In DB2 UDB for OS/390, a string whose actual length, or a varying-length string whose maximum length, is greater than 255 bytes or 127 double-byte characters. Any LOB column, LOB host variable, or expression that evaluates to a LOB is considered a long string.

long table space

A table space that can store only long string or large object (LOB) data.

low-entry networking node (LEN node)

A type 2.1 node that supports independent LU protocols but does not support CP to CP sessions. It can be a peripheral node attached to a boundary node in a subarea network, an end node attached to an APPN network node in an APPN network, or a peer-connected node directly attached to another LEN node or APPN end node.

LPL

See logical page list.

LRECP

See logical recovery pending.

LRH

In DB2 UDB for OS/390, log record header.

LRSN

See log record sequence number.

LU

See logical unit.

LU name

In an OS/390 environment, the name by which VTAM refers to a node in a network. Contrast with location name.

LU 6.2

See logical unit 6.2.

LU type

The classification of a logical unit in terms of the specific subset of SNA protocols and options that it supports for a given session, specifically:

The values allowed in the session activation request
The usage of data stream controls, function management headers, request unit parameters, and sense data values
Presentation services protocols such as those associated with function management headers

LUW

See logical unit of work.

LUWID

See logical unit of work identifier.

M

mapped conversation

In APPC, a conversation between two transaction programs (TPs) using the APPC mapped conversation API. In typical situations, end-user TPs use mapped conversation, and service TPs use basic conversations. Either type of program can use either type of conversation. Contrast with basic conversation.

masking character

A character used to represent optional characters at the front, middle, and end of a search term. Masking characters are normally used for finding variations of a term in a precise index.

materialize

In DB2 UDB for OS/390, (1) The process of putting rows from a view or nested table expression into a work file for additional processing by a query.

(2) The placement of an LOB value into contiguous storage. Because LOB values can be very large, DB2 UDB for OS/390 avoids materializing LOB data until doing so becomes absolutely necessary.

MBCS

See multi-byte character set.

member

(1) For DB2, subscription-set member.

(2) In the OLAP Starter Kit, a method of referencing data through three or more dimensions. An individual data value in a fact table is the intersection of one member from each dimension.

member name

The XCF identifier for a particular DB2 UDB for OS/390 subsystem in a data sharing group.

member scope

See command scope.

menu

In DB2 UDB for OS/390, a displayed list of available functions for selection by the operator. A menu is sometimes called a menu panel.

metadata

Data that describes the characteristics of stored data; descriptive data. For example, the metadata for a database table might include the name of the table, the name of the database that contains the table, the names of the columns in the table, and the column descriptions, either in technical terms or business terms.

metadata publication process

A process created by the Data Warehouse Center that contains all the steps created after publication to keep the published metadata synchronized with the original metadata.

migration

(1) The process of moving data from one computer system to another without converting the data.

(2) Installation of a new version or release of a program to replace an earlier version or release.

(3) The process of converting an existing DB2 UDB for OS/390 subsystem to an updated or current release. In this process, you can acquire the functions of the updated or current release without losing the data that you created on the previous release.

mixed-character string

A string containing a mixture of single-byte and multi-byte characters. Also called mixed data string.

mixed-data string

See mixed-character string.

mobile client

The node, usually a laptop computer, where the mobile enabler, replication source, and target tables used in a mobile environment are located. The mobile replication mode is invoked from the mobile client.

mobile replication enabler

A replication program that starts the mobile replication mode at the mobile client.

mobile replication mode

A mode of replication in which the Capture and Apply programs operate as needed rather than autonomously and continuously. This mode is invoked from the mobile client and allows data to be replicated when the mobile client is available for a connection to the source or target server.

mode

In the Data Warehouse Center, the stage of development of a step, such as development, test, or production.

MODEENT

In an OS/390 environment, a VTAM macro instruction that associates a logon mode name with a set of parameters that represent session protocols. A set of MODEENT macro instructions defines a logon mode table.

modeled statistics

Statistics for a database object that may or may not be referenced in an SQL statement, yet currently exist in an explain model. The object may or may not currently exist in the database.

mode name

(1) In APPC, the name used by the initiator of a session to designate the characteristics desired for the session, such as message length limits, sync point, class of service within the transport network, and session routing and delay characteristics.

(2) In an OS/390 environment, a VTAM name for the collection of physical and logical characteristics and attributes of a session.

modify locks

In DB2 UDB for OS/390, an L-lock or P-lock with a MODIFY attribute. A list of these active locks is kept at all times in the coupling facility lock structure. If the requesting subsystem fails, that subsystem's modify locks are converted to retained locks.

monitoring session

The act of monitoring a database manager or of playing back information from a previously monitored database manager. The DB2 Performance Monitor is used for creating a monitoring session and for selecting which database objects to monitor.

monitor switch

Database manager parameters manipulated by the user to control the type of information and the quantity of information returned in performance snapshots.

MPP

(1) Massively parallel processing.

(2) In an OS/390 environment with IMS, message processing program.

MSS

In an OS/390 environment, Mass Storage Subsystem.

MTO

In an OS/390 environment, master terminal operator.

multi-byte character set (MBCS)

A set of characters in which each character is represented by 2 or more bytes. Character sets that use only two bytes are more commonly known as double-byte character sets.

multidimensional

In the OLAP Starter Kit, a method of referencing data through three or more dimensions. An individual data value in a fact table is the intersection of one member from each dimension.

multidimensional database

In the OLAP Starter Kit, a nonrelational database into which you copy relational data for OLAP analysis.

multi-site update

In DB2 UDB for OS/390, distributed relational database processing in which data is updated in more than one location within a single unit of work.

multitasking

A mode of operation that provides for concurrent performance or interleaved execution of two or more tasks.

must-complete

A state during DB2 UDB for OS/390 processing in which the entire operation must be completed to maintain data integrity.

MVS

Multiple Virtual Storage, which is part of OS/390.

MVS/ESA

Multiple Virtual Storage/Enterprise Systems Architecture, which is part of OS/390.

N

NAU

See network addressable unit.

NDS

See Network Directory Services.

negotiable lock

In DB2 UDB for OS/390, a lock whose mode can be downgraded, by agreement among contending users, to be compatible to all. A physical lock is an example of a negotiable lock.

nested table expression

(1) A result table obtained directly or indirectly from one or more other tables through the evaluation of a fullselect that is specified in the FROM clause.

(2) In DB2 UDB for OS/390, a subselect in a FROM clause (surrounded by parentheses).

NETID

Network identifier. See network name.

network address

An identifier for a node in a network.

network addressable unit (NAU)

The origin or the destination of information transmitted by the path control network. An NAU may be a logical unit (LU), physical unit (PU), control point (CP), or system services control point (SSCP). See also network name.

Network Directory Services (NDS)

A global, distributed, replicated database NetWare that maintains information about, and provides access to, every resource on the network. The NetWare Directory database organizes objects, independent of their physical location, in a hierarchical tree structure called the directory tree.

network identifier (NID)

In an OS/390 environment, the network ID that is assigned by IMS or CICS, or if the connection type is RRSAF, the OS/390 RRS unit of recovery ID (URID).

network name

In SNA, a symbolic name by which end users refer to a network addressable unit (NAU), a link station, or a link. Synonym for NETID.

network node (NN)

In APPN, a node on the network that provides distributed directory services, topology database exchanges with other APPN network nodes, and session and routing services. Synonym for APPN network node.

network node server

An APPN network node that provides network services for its local logical units and adjacent end nodes.

network-qualified name

The name by which an LU is known throughout an interconnected SNA network. A network-qualified name consists of a network name identifying the individual subnetwork, and a network LU name. Network-qualified names are unique throughout an interconnected network. Also known as the network-qualified LU name, or fully qualified LU name.

network services

The services within network addressable units that control network operation through SSCP-to-SSCP, SSCP-to-PU, SSCP-to-LU, and CP-to-CP sessions.

nickname

(1) An identifier that a federated server uses to refer to a data source table or view.

(2) A name that is defined in a DB2 DataJoiner database to represent a physical database object (such as a table or stored procedure) in a non-IBM database.

NID

See network identifier.

NN

See network node.

node

(1) In database partitioning, a synonym for database partition.

(2) In hardware, a uniprocessor or symmetric multiprocessor (SMP) computer that is part of a clustered system or a massively parallel processing (MPP) system. For example, RS/6000 SP is an MPP system that consists of a number of nodes connected by a high-speed network.

(3) In communications, an end point of a communications link, or a junction common to two or more links in a network. Nodes can be processors, communication controllers, cluster controllers, terminals, or workstations. Nodes can vary in routing and other functional capabilities.

node directory

A directory that contains information necessary to establish communications from a client workstation to all applicable database servers.

nodegroup

A named group of one or more database partitions.

noncomplete CCD table

In DB2 replication, a CCD table that is empty when it is created and has rows appended to it as changes are made to the source. Contrast with complete CCD table.

noncondensed attribute

A table attribute indicating that the table contains a history of changes to the data, not current data. A table that has this attribute set includes more than one row for each key value.

noncondensed CCD table

In DB2 replication, a CCD table that contains the history of changes to the values for a row. This type of table is useful for auditing purposes. Contrast with condensed CCD table.

nondelimited ASCII (ASC) format

A file format used to import data. Nondelimited ASCII is a sequential ASCII file with row delimiters used for data exchange with any ASCII product.

nonleaf page

In DB2 UDB for OS/390, a page that contains keys and page numbers of other pages in the index (either leaf or nonleaf pages). Nonleaf pages never point to actual data. Contrast with leaf page.

nonpartitioning index

In DB2 UDB for OS/390, any index that is not a partitioning index.

normalization

In databases, the process of restructuring a data model by reducing its relations to their simplest forms.

not-deterministic function

In DB2 UDB for OS/390, a user-defined function whose result is not solely dependent on the values of the input arguments. Successive invocations with the same argument values can produce a different answer. This type of function is sometimes called a variant function. Contrast with a deterministic function (sometimes called a not-variant function), which always produces the same result for the same input.

not-fenced

A type of user-defined function or stored procedure that is defined to be run in the DBMS process. Contrast with fenced.

notification process

A process created by the Data Warehouse Center that contains all the steps created for notification when a step completes.

not-variant function

A user-defined function whose result is solely dependent on the values of the input arguments. Successive invocations with the same argument values always produce the same results. Contrast with variant function.

NRE

In an OS/390 environment, network recovery element.

NSAPI

Netscape API.

NUL

In C language, a single character that denotes the end of the string.

NULLIF

In DB2 UDB for OS/390, a scalar function that evaluates two passed expressions, returning either NULL if the arguments are equal or the value of the first argument if they are not.

null

In DB2 UDB for OS/390, a value that indicates the absence of information.

nullable

The condition in which a value for a column, function parameter, or result can have an absence of a value. For example, a field for a person's middle initial does not require a value and is considered nullable.

null value

A parameter position for which no value is specified.

NUL-terminated host variable

In DB2 UDB for OS/390, a varying-length host variable in which the end of the data is indicated by the presence of a NUL terminator.

NUL terminator

In C language, the value that indicates the end of a string. For character strings, the NUL terminator is X'00'.

O

OASN (origin application schedule number)

In an OS/390 environment with IMS, a 4-byte number that is assigned sequentially to each IMS schedule since the last cold start of IMS. The OASN is used as an identifier for a unit of work. In an 8-byte format, the first 4 bytes contain the schedule number and the last 4 bytes contain the number of IMS sync points (commit points) during the current schedule. The OASN is part of the NID for an IMS connection.

OBID

In DB2 UDB for OS/390, data object identifier.

object

(1) Anything that can be created or manipulated with SQL--for example, tables, views, indexes, or packages.

(2) In object-oriented design or programming, an abstraction consisting of data and operations associated with that data.

(3) For NetWare, an entity that is defined on the network and thus given access to the file server.

object property

A property that identifies a category of information that is associated with an object. A NetWare bindery object can be assigned one or more properties. The DB2 server instance object has an object property, NET_ADDR, which denotes the location of the record within the object.

object type

(1) A 2-byte number that classifies an object in the bindery on a NetWare file server. 062B represents the DB2 database server object type.

(2) A categorization or grouping of object instances that share similar behaviors and characteristics.

ODBC

See Open Database Connectivity.

ODBC driver

A driver that implements ODBC function calls and interacts with a data source.

offline backup

A backup of the database or table space that was made when the database or table space was not being accessed by applications. The Backup Database utility acquires exclusive use of the database until the backup is complete. Contrast with online backup.

offline restore

A restoration of a copy of a database or table space from a backup. The Backup Database utility has exclusive use of the database until the restore is completed. Contrast with online restore.

OLAP

See online analytical processing.

on-demand timing

A method for controlling the timing of replication for occasionally connected systems. Requires that you use the ASNSAT program to operate the Capture and Apply programs. Contrast with event timing and interval timing.

online analytical processing (OLAP)

In the OLAP Starter Kit, a multidimensional, multi-user, client server computing environment for users who need to analyze consolidated enterprise data in real time.

online backup

A backup of the database or table space that is made while the database or table space is being accessed by other applications. Contrast with offline backup.

online monitor

See Performance Monitor.

online restore

A restoration of a copy of a database or table space while the database or table space is being accessed by other applications. Contrast with offline restore.

Open Database Connectivity (ODBC)

An API that allows access to database management systems using callable SQL, which does not require the use of an SQL preprocessor. The ODBC architecture allows users to add modules, called database drivers, that link the application to their choice of database management systems at run time. Applications do not need to be linked directly to the modules of all the supported database management systems.

operand

An entity on which an operation is performed.

optimized SQL text

SQL text, produced by the Explain facility, that is based on the query actually used by the optimizer to choose the access plan. This query is supplemented and rewritten by the various components of the SQL compiler during statement compilation. The text is reconstructed from its internal representation, and differs from the original SQL text. The optimized statement produces the same result as the original statement.

optimizer

A component of the SQL compiler that chooses an access plan for a data manipulation language statement by modeling the execution cost of many alternative access plans and choosing the one with the minimal estimated cost.

ordinary identifier

(1) In SQL, a letter followed by zero or more characters, each of which is a letter (a-z and A-Z), a symbol, a number, or the underscore character, used to form a name.

(2) In DB2 UDB for OS/390, an uppercase letter followed by zero or more characters, each of which is an uppercase letter, a number, or the underscore character. An ordinary identifier must not be a reserved word.

ordinary token

A numeric constant, an ordinary identifier, a host identifier, or a keyword.

originating task

In DB2 UDB for OS/390, the primary agent in a parallel group that receives data from other execution units (referred to as parallel tasks) that are executing portions of the query in parallel.

outer join

(1) A join method in which a column that is not common to all of the tables being joined becomes part of the resultant table. Contrast with inner join.

(2) In DB2 UDB for OS/390, the result of a join operation that includes the matched rows of both tables that are being joined and preserves some or all of the unmatched rows of the tables that are being joined. See also join.

outline

In the OLAP Starter Kit, the structure that defines all elements of a database within the OLAP Starter Kit. For example, an outline contains definitions of dimensions, members, and formulas.

output file

A database or device file that is opened with the option to allow the writing of records.

overflow record

(1) On an indirectly addressed file, a record whose key is randomized to the address of a full track or to the address of a home record.

(2) In DB2, an updated record that is too large to fit on the page it is currently stored in. The record is copied to a different page and its original location is replaced with a pointer to the new location.

(3) In the Database Monitor, a record inserted in the event monitor data stream to indicate that records were discarded because the named pipe was full and records were not processed in time. An overflow record indicates how many records were discarded.

overloaded function name

A function name for which multiple functions exist within a function path or schema. Those within the same schema must have different signatures.

P

package

A control structure produced during program preparation that is used to execute SQL statements.

package list

In DB2 UDB for OS/390, an ordered list of package names that can be used to extend an application plan.

package name

In DB2 UDB for OS/390, the name of an object that is created by a BIND PACKAGE or REBIND PACKAGE command. The object is a bound version of a database request module (DBRM). The name consists of a location name, a collection ID, a package ID, and a version ID.

packet

In data communication, a sequence of binary digits, including data and control signals, that is transmitted and switched as a composite whole.

page

(1) A block of storage within a table or index whose size is 4096 bytes (4 KB).

(2) In DB2 UDB for OS/390, a unit of storage within a table space (4 KB, 8 KB, 16 KB, or 32 KB) or index space (4 KB). In a table space, a page contains one or more rows of a table. In an LOB table space, an LOB value can span more than one page, but no more than one LOB value is stored on a page.

page set

In an OS/390 environment, another way to refer to a table space or index space. Each page set consists of a collection of VSAM data sets.

page set recovery pending (PSRCP)

In DB2 UDB for OS/390, a restrictive state of an index space in which the entire page set must be recovered. Recovery of a logical part is prohibited.

panel

In DB2 UDB for OS/390, a predefined display image that defines the locations and characteristics of display fields on a display surface (for example, a menu panel).

parallel group

In an OS/390 environment, a set of consecutive operations that execute in parallel and that have the same number of parallel tasks.

parallel I/O

The process of reading from or writing to two or more I/O devices at the same time to reduce response time.

parallel I/O processing

A form of I/O processing in which DB2 UDB for OS/390 initiates multiple concurrent requests for a single user query and performs I/O processing concurrently (in parallel) on multiple data partitions.

parallelism

The ability to perform multiple database operations at the same time (in parallel). See inter-partition parallelism, intra-partition parallelism, and parallel I/O.

parallel session

In SNA, two or more concurrently active sessions between the same two logical units. Each session can have different session parameters. See session.

Parallel Sysplex

A set of OS/390 systems that communicate and cooperate with each other through certain multisystem hardware components and software services.

parallel task

In an OS/390 environment, the execution unit that is dynamically created to process a query in parallel. It is implemented by an MVS service request block.

parameterized data type

A data type that can be defined with a specific length, scale, or precision. String and decimal data types are parameterized.

parameter marker

A question mark (?) that appears in a statement string of a dynamic SQL statement. The question mark can appear where a host variable might appear if the statement string was a static SQL statement.

parent key

A primary key or unique key that is used in a referential constraint. The values of a parent key determine the valid values of the foreign key in the constraint.

parent row

A row that has at least one dependent row.

parent table

A table that is a parent in at least one referential constraint.

parent table space

In DB2 UDB for OS/390, a table space that contains a parent table. A table space that contains a dependent of that table is a dependent table space.

participant

In an OS/390 environment, an entity other than the commit coordinator that takes part in the commit process. Synonym for agent in SNA.

partition

In an OS/390 environment, a portion of a page set. Each partition corresponds to a single, independently extendable data set. Partitions can be extended to a maximum size of 1, 2, or 4 GB, depending on the number of partitions in the partitioned page set. All partitions of a given page set have the same maximum size.

partition compatible join

A join where all of the rows that are joined reside in the same database partition.

partitioned database

A database with two or more database partitions. Data in user tables can be located in one or more database partitions. When a table is on multiple partitions, some of its rows are stored in one partition and others are stored in other partitions. See database partition.

partitioned data set (PDS)

In an OS/390 environment, a data set in direct-access storage that is divided into partitions, which are called members. Each partition can contain a program, part of a program, or data. Synonym for program library.

partitioned page set

In an OS/390 environment, a partitioned table space or index space. Header pages, space map pages, data pages, and index pages refer to data only within the scope of the partition.

partitioned table space

In an OS/390 environment, a table space that is subdivided into parts (based on index key range), each of which can be processed independently by utilities.

partitioned function

A function that takes a partitioning key value of a row as input and produces a partition number as output.

partitioning key

(1) An ordered set of one or more columns in a given table. For each row in the table, the values in the partitioning key columns are used to determine on which database partition the row belongs.

(2) In replication, an ordered set of one or more columns in a given table. For each row in the source table, the values in the partitioning key columns are used to determine in which target table the row belongs.

partitioning map

A vector of partition numbers that maps a partitioning map index to database partitions in the nodegroup.

partitioning map index

A number assigned to a hash partition or range partition.

partner logical unit (LU)

(1) In SNA, the remote participant in a session.

(2) An access point in the SNA network that is connected to the local DB2 UDB for OS/390 subsystem by way of a VTAM conversation.

pass-through

In a federated database system, a facility by which users can communicate with data sources in the SQL dialect of the data source.

path

See SQL path.

PCT

In CICS, program control table.

PDS

See partitioned data set.

peer-to-peer communication

Communication between two SNA logical units (LUs) that is not managed by a host; commonly used when referring to LU 6.2 nodes.

performance metrics

A collection of all performance variables belonging to the same database object.

Performance Monitor

A tool that lets database administrators use a graphical interface to monitor the performance of a DB2 system for tuning purposes. This tool can be accessed from the Control Center.

performance snapshot

Performance data for a set of database objects that is retrieved from the database manager at a point in time.

performance variable

A statistic derived from performance data obtained from the database manager. The expression for this variable can be user defined.

performance variable profile

A flat file that contains definitions of performance variables. This file can be edited, copied, and shared. Different profiles can be used by the same Performance Monitor so that different calculations can be performed.

persistence

In Net.Data, the state of keeping an assigned value for an entire transaction, where a transaction spans multiple Net.Data invocations. Only variables can be persistent. In addition, operations on resources affected by commitment control are kept active until an explicit commit or rollback is done, or when the transaction completes.

phantom row

A table row that can be read by application processes that are executing with any isolation level except repeatable read. When an application process issues the same query multiple times within a single unit of work, additional rows can appear between queries because of the data being inserted and committed by application processes that are running concurrently.

physical claim

In DB2 UDB for OS/390, a claim on an entire nonpartitioning index.

physical consistency

In DB2 UDB for OS/390, the state of a page that is not in a partially changed state.

physical drain

In DB2 UDB for OS/390, a drain on an entire nonpartitioning index.

physical lock (P-lock)

A lock type that DB2 UDB for OS/390 acquires to provide consistency of data that is cached in different DB2 UDB for OS/390 subsystems. Physical locks are used only in data sharing environments. Contrast with logical lock (L-lock).

physical lock contention

In DB2 UDB for OS/390, conflicting states of the requesters for a physical lock. See also negotiable lock.

physically complete

In DB2 UDB for OS/390, the state in which the concurrent copy process is completed and the output data set has been created.

physical unit (PU)

The component that manages and monitors the resources (such as attached links and adjacent link stations) associated with a node, as requested by an SSCP through an SSCP-to-PU session. An SSCP activates a session with the PU in order to indirectly manage, through the PU, resources of the node such as attached links. This term applies to types 2.0, 4, and 5 nodes only. See also control point.

piece

In an OS/390 environment, a data set of a nonpartitioned page set.

plan

See application plan.

plan allocation

The process of allocating DB2 UDB for OS/390 resources to a plan in preparation to execute it.

plan name

In DB2 UDB for OS/390, the name of an application plan.

plan segmentation

In DB2 UDB for OS/390, the dividing of each plan into sections. When a section is needed, it is independently brought into the EDM pool.

P-lock

See physical lock.

PLT

In CICS, program list table.

point-in-time table

In DB2 replication, a type of target table whose content matches all or part of a source table, with an added system column that identifies the approximate time when the particular row was inserted or updated at the source system.

point of consistency

A point in time when all the recoverable data a program accesses is consistent. The point of consistency occurs when updates, inserts, and deletions are either committed to the physical database or rolled back. Synonym for commit point and sync point.

policy

See CFRM policy.

postponed abort UR

In DB2 UDB for OS/390, a unit of recovery that was inflight or in-abort, was interrupted by system failure or cancellation, and did not complete backout during restart.

PPT

(1) In CICS, processing program.

(2) In OS/390, program properties table.

precision

In numeric data types, the total number of binary or decimal digits, excluding the sign.

precompile

To process programs that contain SQL statements before they are compiled. SQL statements are replaced with statements that will be recognized by the host language compiler. The output from a precompile process includes source code that can be submitted to the compiler and used in the bind process.

predicate

An element of a search condition that expresses or implies a comparison operation.

prefetch

To read data ahead of, and in anticipation of, its use.

prepare

(1) To convert an SQL statement from text form to an executable form, by submitting it to the SQL compiler.

(2) In DB2 UDB for OS/390, the first phase of a two-phase commit process in which all participants are requested to prepare for commit.

prepared SQL statement

In SQL, a named object that is the executable form of an SQL statement that has been processed by the PREPARE statement.

primary authorization ID

The authorization ID used to identify the application process to DB2 UDB for OS/390.

primary group buffer pool

For a duplexed group buffer pool, the DB2 UDB for OS/390 structure that is used to maintain the coherency of cached data. This structure is used for page registration and cross-invalidation. The OS/390 equivalent is old structure. Compare with secondary group buffer pool.

primary index

In DB2 UDB for OS/390, an index that enforces the uniqueness of a primary key.

primary key

A unique key that is part of the definition of a table. A primary key is the default parent key of a referential constraint definition.

primary log

A set of one or more log files used to record changes to a database. Storage for these files is allocated in advance. Contrast with secondary log.

principal

In an OS/390 environment, an entity that can communicate securely with another entity. In the DCE, principals are represented as entries in the DCE registry database and include users, servers, computers, and others.

principal name

In an OS/390 environment, the name by which a principal is known to the DCE security services.

private connection

A communications connection that is specific to DB2 UDB for OS/390.

private protocol access

A method of accessing distributed data by which you can direct a query to another DB2 system. Contrast with DRDA access.

private protocol connection

A DB2 private connection of the application process. See also private connection.

privilege

(1) The right to access a specific database object in a specific way. These rights are controlled by users with SYSADM (system administrator) authority or DBADM (database administrator) authority or by creators of objects. Privileges include rights such as creating, deleting, and selecting data from tables.

(2) In DB2 UDB for OS/390, the capability of performing a specific function, sometimes on a specific object. See also explicit privilege and implicit privilege.

privilege set

For the installation SYSADM ID, the set of all possible privileges. For any other authorization ID, the set of all privileges that are recorded for that ID in the DB2 UDB for OS/390 catalog.

procedure

See stored procedure.

process

(1) In the Data Warehouse Center, a series of steps, which commonly operates on source data, that changes data from its original form into a form conducive to decision support. A Data Warehouse Center process commonly consists of one or more sources, one or more steps, and one or more targets.

(2) In DB2 UDB for OS/390, the unit to which DB2 UDB for OS/390 allocates resources and locks. A process involves the execution of one or more programs. The execution of an SQL statement is always associated with some process. The means of initiating and terminating a process are dependent on the environment. Synonym for application process.

property

In the Data Warehouse Center, a characteristic or attribute that describes a unit of information. Each object type has a set of associated properties. For each object, a set of values is assigned to the properties.

protected conversation

In an OS/390 environment, a VTAM conversation that supports two-phase commit flows.

protocol.ini

A file that contains LAN configuration and binding information for all the protocol and medium-access control (MAC) system modules.

PSRCP

In DB2 UDB for OS/390, page set recovery pending.

PU

See physical unit.

public authority

The authority for an object granted to all users.

PU type

In SNA, the classification of a physical unit according to the type of node on which it resides.

Q

QSAM

Queued sequential access method.

quantified predicate

A predicate that compares a value with a set of values.

query

(1) A request for information from the database based on specific conditions, for example, a request for a list of all customers in a customer table whose balance is greater than $1000.

(2) In DB2 UDB for OS/390, a component of certain SQL statements that specifies a result table.

query block

In DB2 UDB for OS/390, the part of a query that is represented by one of the FROM clauses. Each FROM clause can have multiple query blocks, depending on how DB2 UDB for OS/390 internally processes the query.

Query by Image Content (QBIC)

A capability that is provided by the Image Extender that allows users to search images by their visual characteristics, such as average color and texture.

query CP parallelism

In DB2 UDB for OS/390, parallel execution of a single query, which is accomplished by using multiple tasks. Compare with Sysplex query parallelism.

query I/O parallelism

In DB2 UDB for OS/390, parallel access of data, which is accomplished by triggering multiple I/O requests within a single query.

queued sequential access method (QSAM)

An extended version of the basic sequential access method (BSAM). When this method is used, a queue is formed of input data blocks that are awaiting processing or of output data blocks that are awaiting transfer to auxiliary storage or to an output device.

quiesce

To end a process by allowing operations to complete normally, while rejecting any new requests for work.

quiesced member state

In DB2 UDB for OS/390, a state of a member of a data sharing group. An active member becomes quiesced when a STOP DB2 command takes effect without a failure. If the member task, address space, or OS/390 system fails before the command takes effect, the member state is failed.

quoted name

See delimited identifier.

R

RACF

In an OS/390 environment, Resource Access Control Facility.

RAMAC

In an OS/390 environment, the IBM family of enterprise disk storage system products.

RBA

See relative byte address.

RCT

In DB2 UDB for OS/390 with the CICS attachment facility, the resource control table.

RDB

See relational database.

RDBMS

See relational database management system.

RDBNAM

See relational database name.

RDF

In DB2 UDB for OS/390, record definition field.

read stability (RS)

An isolation level that locks only the rows that an application retrieves within a transaction. Read stability ensures that any qualifying row that is read during a transaction is not changed by other application processes until the transaction is completed, and that any row changed by another application process is not read until the change is committed by that process. Read stability allows more concurrency than repeatable read, and less than cursor stability.

rebind

To create a package for an application program that was previously bound. For example, if an index is added for a table that is accessed by a program, the package must be rebound for it to take advantage of the new index.

record

The storage representation of a single row of a table or other data.

record identifier (RID)

A number that is used internally by DB2 to uniquely identify a record in a table. The RID contains enough information to address the page in which the record is stored. Compare with row ID.

record identifier (RID) pool

In DB2 UDB for OS/390, an area of main storage above the 16-MB line that is reserved for sorting record identifiers during list prefetch processing.

recording

The information from performance snapshots that can be viewed at a later time.

recoverable log

A database log in which all log records are retained so that, in the event of a failure, lost data can be recovered during forward recovery. Contrast with circular log.

recovery

(1) The act of resetting a system, or data that is stored in a system, to an operable state following damage.

(2) The process of rebuilding databases by restoring a backup and rolling forward the logs associated with it.

recovery log

See database log.

recovery pending

A state of the database or table space. A database or table space is put in recovery pending state when it is restored from a backup. While the database or table space is in this state, its data cannot be accessed.

recovery token

In DB2 UDB for OS/390, an identifier for an element that is used in recovery (for example, NID or URID).

RECP

In DB2 UDB for OS/390, recovery pending.

recursion cycle

The cycle that occurs when a fullselect within a common table expression includes the name of the common table expression in a FROM clause.

recursive common table expression

A common table expression that refers to itself in a FROM clause from the fullselect. Recursive common table expressions are used to write recursive queries.

recursive query

A fullselect that uses a recursive common table expression.

redo

In DB2 UDB for OS/390, a state of a unit of recovery that indicates that changes are to be reapplied to the DASD media to ensure data integrity.

referential constraint

The referential integrity rule that the nonnull values of the foreign key are valid only if they also appear as values of a parent key.

referential integrity

(1) The state of a database in which all values of all foreign keys are valid.

(2) The condition that exists when all intended references from data in one column of a table to data in another column of the same or a different table are valid. Maintaining referential integrity requires that DB2 UDB for OS/390 enforce referential constraints on all LOAD, RECOVER, INSERT, UPDATE, and DELETE operations.

referential structure

In DB2 UDB for OS/390, a set of tables and relationships that includes at least one table and, for every table in the set, all the relationships in which that table participates and all the tables to which it is related.

refresh

A process in which all of the data of interest in a user table is copied to the target table, replacing existing data. See also full refresh and differential refresh.

registration

See replication source.

registration process

In DB2 replication, the process of defining a replication source. Contrast with subscription process.

registry database

In an OS/390 environment, a database of security information about principals, groups, organizations, accounts, and security policies. The DCE security component maintains the registry database.

regular table space

A table space that can store any nontemporary data.

rejected transaction

In DB2 replication, a transaction that contains one or more updates from replica tables that are out of date in comparison to the source table.

relational cube

A set of data and metadata that together define a multidimensional database. A relational cube is the portion of a multidimensional database that is stored in a relational database. See also multidimensional database.

relational database

A database that can be perceived as a set of tables and manipulated in accordance with the relational model of data.

relational database management system (RDBMS)

In DB2 UDB for OS/390, a collection of hardware and software that organizes and provides access to a relational database.

relational database name (RDBNAM)

A unique identifier for an RDBMS within a network. In DB2 UDB for OS/390, this must be the value in the LOCATION column of table SYSIBM.LOCATIONS in the CDB. DB2 UDB for OS/390 publications refer to the name of another RDBMS as a LOCATION value or a location name.

relationship

In DB2 UDB for OS/390, a defined connection between the rows of a table or the rows of two tables. A relationship is the internal representation of a referential constraint.

relative byte address (RBA)

In an OS/390 environment, the offset of a data record or control interval from the beginning of the storage space that is allocated to the data set or file to which it belongs.

remigration

The process of returning to a current release of DB2 UDB for OS/390 following a fallback to a previous release. This procedure constitutes another migration process.

remote

In DB2 UDB for OS/390, any object that is maintained by a remote DB2 subsystem. A remote view, for example, is a view that is maintained by a remote DB2 subsystem. Contrast with local.

remote attach request

In DB2 UDB for OS/390, a request made by a remote location to attach to the local DB2 subsystem. Specifically, the request that is sent is an SNA Function Management Header 5.

remote database

A database that is physically located on a workstation other than the one in use. Contrast with local database.

remote subsystem

In DB2 UDB for OS/390, any RDBMS, except the local subsystem, with which the user or application can communicate. The subsystem need not be remote in any physical sense, and might even operate on the same processor under the same OS/390 system.

remote unit of work (RUOW)

A unit of work that allows for the remote preparation and execution of SQL statements.

reoptimization

The DB2 UDB for OS/390 process of reconsidering the access path of an SQL statement at run time; during reoptimization, DB2 UDB for OS/390 uses the values of host variables, parameter markers, or special registers.

REORG pending (REORP)

In DB2 UDB for OS/390, a condition that restricts SQL access and most utility access to an object that must be reorganized.

REORP

See REORG pending.

repeatable read (RR)

An isolation level that locks all the rows in an application that are referenced within a transaction. When a program uses repeatable read protection, rows referenced by the program cannot be changed by other programs until the program ends the current transaction.

replica

A type of target table that can be updated locally and receives updates from a user table through a subscription definition. It can be a source for updating the user table or read-only target tables.

replica target table

A replication table at the target server that is a type of update-anywhere target table.

replication

The process of maintaining a defined set of data in more than one location. It involves copying designated changes for one location (a source) to another (a target), and synchronizing the data in both locations.

replication administrator

The user responsible for defining replication sources and subscriptions. This user can also run the Capture and Apply programs.

replication source

A database table or view that can accept copy requests and is the source table in a subscription set. See also subscription set.

replication subscription

A specification for copying changed data from replication sources to target tables at a specified time and frequency, with the option of enhancing data. It defines all of the information that is required by the Apply program to copy data.

request commit

In DB2 UDB for OS/390, the vote that is submitted to the prepare phase if the participant has modified data and is prepared to commit or roll back.

requester

In DB2 UDB for OS/390, the source of a request to a remote RDBMS, the system that requests the data. Synonym for application requester.

reserved word

(1) A word used in a source program to describe an action to be taken by the program or compiler. It must not appear in the program as a user-defined name or a system name.

(2) A word that has been set aside for special use in the SQL standard.

resource

In DB2 UDB for OS/390, the object of a lock or claim, which could be a table space, an index space, a data partition, an index partition, or a logical partition.

resource allocation

In DB2 UDB for OS/390, the part of plan allocation that deals specifically with the database resources.

resource control table (RCT)

In DB2 UDB for OS/390 with CICS, a construct of the CICS attachment facility, created by site-provided macro parameters, that defines authorization and access attributes for transactions or transaction groups.

resource definition online

In an OS/390 environment with CICS, a feature that you use to define CICS resources online without assembling tables.

resource limit facility (RLF)

A portion of DB2 UDB for OS/390 code that prevents dynamic manipulative SQL statements from exceeding specified time limits. Synonym for governor.

resource limit specification table

In DB2 UDB for OS/390, a site-defined table that specifies the limits to be enforced by the resource limit facility.

restart pending (RESTP)

In DB2 UDB for OS/390, a restrictive state of a page set or partition that indicates that restart (backout) work needs to be performed on the object. All access to the page set or partition is denied except for access by the RECOVER POSTPONED command or the automatic online backout, which DB2 UDB for OS/390 invokes after restart if the system parameter LBACKOUT=AUTO.

RESTP

See restart pending.

restore

To return a backup copy to the active storage location for use.

restore set

A backup copy of a database or table space plus zero or more log files that, when restored and rolled forward, bring the database or table space back to a consistent state.

result set

The set of rows that a stored procedure returns.

result set locator

A 4-byte value that DB2 UDB for OS/390 uses to uniquely identify a query result set that a stored procedure returns.

result table

The set of rows produced by the evaluation of a SELECT statement.

retained lock

A MODIFY lock that a DB2 UDB for OS/390 subsystem was holding at the time of a subsystem failure. The lock is retained in the coupling facility lock structure across a DB2 UDB for OS/390 failure.

revoke

To remove a privilege or authority from an authorization ID.

RID

See record identifier.

RID pool

See record identifier pool.

right outer join

In DB2 UDB for OS/390, the result of a join operation that includes the matched rows of both tables that are being joined and preserves the unmatched rows of the second join operand. See join.

RLF

See resource limit facility.

RO

In DB2 UDB for OS/390, read-only access.

rollback

The process of restoring data changed by SQL statements to the state at its last commit point. See point of consistency.

roll-forward

The process of updating the data in a restored database by applying changes recorded in the database log. See forward recovery.

root page

In DB2 UDB for OS/390, the page of an index page set that follows the first index space map page. A root page is the highest level (or the beginning point) of the index.

routine

In DB2 UDB for OS/390, a user-defined function or a stored procedure.

row

The horizontal component of a table consisting of a sequence of values, one for each column of the table.

ROWID

See row identifier.

row identifier (ROWID)

In DB2 UDB for OS/390, a value that uniquely identifies a row. This value is stored with the row and does not change.

row lock

In DB2 UDB for OS/390, a lock on a single row of data.

row-replica

In DB2 replication, a type of update-anywhere replica maintained by DataPropagator for Microsoft Jet without transaction semantics.

row-replica conflict detection

In DB2 replication, conflict detection that is performed row by row, not transaction by transaction, as is done for DB2 replicas.

row trigger

In DB2 UDB for OS/390, a trigger that is defined with the trigger granularity FOR EACH ROW.

RR

See repeatable read.

RRE

In an OS/390 environment with IMS, residual recovery entry.

RS

See read stability.

RRSAF

Recoverable Resource Manager Services attachment facility, which is a DB2 UDB for OS/390 subcomponent that uses OS/390 Transaction Management and Recoverable Resource Manager Services to coordinate resource commitment between DB2 UDB for OS/390 and all other resource managers that also use OS/390 RRS in an OS/390 system.

RUOW

See remote unit of work.

S

sargable

A predicate that can be evaluated as a search argument.

satellite

An occasionally connected client that has a DB2 server that synchronizes with its group at the satellite control database.

Satellite Administration Center

A user interface that provides centralized administrative support for satellites.

satellite control server

A DB2 Universal Database system that contains the satellite control database, SATCTLDB.

SBCS

See single-byte character set.

SCA

In DB2 UDB for OS/390, the shared communications area.

scalar fullselect

A fullselect that returns a single value--one row of data that consists of exactly one column.

scalar function

An SQL operation that produces a single value from another value and is expressed as a function name followed by a list of arguments enclosed in parentheses. Contrast with column function.

scale

The number of digits in the fractional part of a number.

schema

(1) A collection of database objects such as tables, views, indexes, or triggers. A database schema provides a logical classification of database objects.

(2) In DB2 UDB for OS/390, a logical grouping for user-defined functions, distinct types, triggers, and stored procedures. When an object of one of these types is created, it is assigned to one schema, which is determined by the name of the object.

(3) In the Data Warehouse Center, a collection of warehouse target tables and the relationships between the warehouse target table columns, where the target tables can come from one or more warehouse targets.

SDK

See Software Developer's Kit.

SDWA

In an OS/390 environment, the system diagnostic work area.

search condition

A criterion for selecting rows from a table. A search condition consists of one or more predicates.

secondary authorization ID

In DB2 UDB for OS/390, an authorization ID that is associated with a primary authorization ID by an authorization exit routine.

secondary group buffer pool

For a duplexed group buffer pool in a DB2 UDB for OS/390 environment, the structure that is used to back up changed pages that are written to the primary group buffer pool. No page registration or cross-invalidation occurs using the secondary group buffer pool. The OS/390 equivalent is new structure. Compare to primary group buffer pool.

secondary log

A set of one or more log files used to record changes to a database. Storage for these files is allocated as needed when the primary log is full. Contrast with primary log.

section

In DB2 UDB for OS/390, the segment of a plan or package that contains the executable structures for a single SQL statement. For most SQL statements, one section in the plan exists for each SQL statement in the source program. However, for cursor-related statements, the DECLARE, OPEN, FETCH, and CLOSE statements reference the same section because, they each refer to the SELECT statement that is named in the DECLARE CURSOR statement. SQL statements such as COMMIT, ROLLBACK, and some SET statements do not use a section.

segmented table space

In DB2 UDB for OS/390, a table space that is divided into equal-sized groups of pages called segments. Segments are assigned to tables so that rows of different tables are never stored in the same segment.

self-referencing constraint

In DB2 UDB for OS/390, a referential constraint that defines a relationship in which a table is a dependent of itself.

self-referencing row

A row that is a parent of itself.

self-referencing subquery

A subselect or fullselect within a DELETE, INSERT, or UPDATE statement that refers to the same table that is the object of the SQL statement.

self-referencing table

A table that is both a parent and a dependent table in the same referential constraint.

sequential data set

A non-DB2 UDB for OS/390 data set whose records are organized on the basis of their successive physical positions, such as on magnetic tape. Several of the DB2 UDB for OS/390 database utilities require sequential data sets.

sequential prefetch

In DB2 UDB for OS/390, a mechanism that triggers consecutive asynchronous I/O operations. Pages are fetched before they are required, and several pages are read with a single I/O operation.

server

(1) In a network, a node that provides facilities to other stations, for example, a file server, a printer server, a mail server.

(2) In a federated database system, a unit of information that identifies a data source to a federated server. This information can include the server's name, its type, its version, and the name of the wrapper that the federated server uses to communicate with and retrieve data from the data source.

(3) A functional unit that provides services to one or more clients over a network. In the DB2 UDB for OS/390 environment, a server is the target for a request from a remote RDBMS and is the RDBMS that provides the data. See also application server.

service class

In DB2 UDB for OS/390, an 8-character identifier that is used by MVS Workload Manager to associate customer performance goals with a particular DDF thread or stored procedure. A service class is also used to classify work on parallelism assistants.

service name

A name that provides a symbolic method of specifying the port number to be used at a remote node. The TCP/IP connection requires the address of the remote node and the port number to be used on the remote node to identify an application.

session

A logical connection between two stations or SNA network addressable units (NAUs) that allows the two stations or NAUs to communicate.

session limit

In SNA, the maximum number of concurrently active logical unit to logical unit (LU-to-LU) sessions that a particular logical unit (LU) can support.

session partner

In SNA, one of the two network addressable units (NAUs) participating in an active session.

session protocols

In DB2 UDB for OS/390, the available set of SNA communication requests and responses.

session security

For LU 6.2, partner LU verification and session data encryption. A Systems Network Architecture (SNA) function that allows data to be transmitted in encrypted form.

set operator

The SQL operators UNION, EXCEPT, and INTERSECT corresponding to the relational operators union, difference, and intersection. A set operator derives a result table by combining two other result tables.

shadowing

A recovery technique in which current page contents are never overwritten. Instead, new pages are allocated and written while the pages whose values are being replaced are retained as shadow copies until they are no longer needed to support the restoration of the system state due to a transaction rollback.

shared communications area (SCA)

A coupling facility list structure that a DB2 UDB for OS/390 data sharing group uses for inter-DB2 communication.

shared lock

A lock that limits concurrently executing application processes to read-only operations on database data. Contrast with exclusive lock.

shift-in character

A special control character (X'0F') that is used in EBCDIC systems to denote that the subsequent bytes represent SBCS characters. Contrast with shift-out character.

shift-out character

A special control character (X'0E') that is used in EBCDIC systems to denote that the subsequent bytes, up to the next shift-in control character, represent DBCS characters. Contrast with shift-in character.

short string

(1) A fixed-length string or a variable-length string whose maximum length is less than or equal to 254 bytes.

(2) In DB2 UDB for OS/390, a string whose actual length, or a variable-length string whose maximum length, is 255 bytes (or 127 double-byte characters) or less. Regardless of length, an LOB string is not a short string.

sign-on

A request that is made on behalf of an individual CICS or IMS application process by an attachment facility to enable DB2 UDB for OS/390 to verify that it is authorized to use DB2 UDB for OS/390 resources.

simple page set

In DB2 UDB for OS/390, a nonpartitioned page set. A simple page set initially consists of a single data set (page set piece). If that data set is extended to 2 GB, another data set is created, and so on up to a total of 32 data sets. DB2 UDB for OS/390 considers the data sets to be a single contiguous linear address space that contains a maximum of 64 GB. Data is stored in the next available location within this address space without regard to any partitioning scheme.

simple table space

In DB2 UDB for OS/390, a table space that is neither partitioned nor segmented.

single-byte character set (SBCS)

A character set in which each character is represented by a one-byte code.

single-precision floating point number

A 32-bit approximate representation of a real number.

SMF

In an OS/390 environment, system management facility.

SMS

In an OS/390 environment, Storage Management Subsystem.

SMS table space

See system-managed space table space.

SNA

See Systems Network Architecture.

SNA network

The part of the user application network that conforms to the formats and protocols of Systems Network Architecture (SNA). It enables reliable transfer of data among users and provides protocols for controlling the resources of various network configurations. The SNA network consists of network addressable units (NAUs), gateway function, intermediate session routing function components, and the transport network.

snapshot

See performance snapshot and explain snapshot.

socket

A callable TCP/IP programming interface that is used by TCP/IP network applications to communicate with remote TCP/IP partners.

soft checkpoint

The process of writing some information to the log file header; this information is used to determine the starting point in the log in case a database restart is required.

Software Developer's Kit (SDK)

An application development product that allows applications to be developed on a client workstation to access remote database servers including host relational databases through the DB2 Connect products.

source

In the Data Warehouse Center, a table, view, or file that is input to a step.

source function

A user-defined function (UDF) that is used to implement one or more other UDFs.

sourced function

In DB2 UDB for OS/390, a function that is implemented by another built-in or user-defined function that is already known to the database manager. This function can be a scalar function or a column (aggregating) function; it returns a single value from a set of values (for example, MAX or AVG). Contrast with external function and built-in function.

source program

A set of host language statements and SQL statements that is processed by an SQL precompiler.

source server

In DB2 replication, the database location of the replication source and the Capture program.

source table

In DB2 replication, a table that contains the data that is to be copied to a target table. The source table can be a replication source table, a change data table, or a consistent-change-data table. Contrast with target table.

source type

An existing type that is used to internally represent a distinct type.

special register

A storage area that is defined for an application process by the database manager and is used to store information that can be referenced in SQL statements. Examples are USER and CURRENT DATE.

specific function name

(1) The name that uniquely identifies a function to the system.

(2) In DB2 UDB for OS/390, a particular user-defined function that is known to the database manager by its specific name. Many specific user-defined functions can have the same function name. When a user-defined function is defined to the database, every function is assigned a specific name that is unique within its schema. Either the user can provide this name, or a default name is used.

spill file

In DB2 replication, a temporary file created by the Apply program that is used as the source for updating data to multiple target tables.

Spreadsheet Add-in

In the OLAP Starter Kit, software that merges with Microsoft Excel and Lotus 1-2-3 to allow multidimensional analysis of data. The software library appears as a menu add-in to the spreadsheet and provides such multidimensional analysis features as connect, zoom-in, and calculate.

SPUFI

In DB2 UDB for OS/390, SQL Processor Using File Input.

SQL

See Structured Query Language.

SQL authorization ID (SQL ID)

In DB2 UDB for OS/390, the authorization ID that is used for checking dynamic SQL statements in some situations.

SQLCA

See SQL communication area.

SQL communication area (SQLCA)

A set of variables that provides an application program with information about the execution of its SQL statements or its requests from the database manager.

SQL connection

In DB2 UDB for OS/390, an association between an application process and a local or remote application server.

SQLDA

See SQL descriptor area.

SQL descriptor area (SQLDA)

(1) A set of variables that is used in the processing of certain SQL statements. The SQLDA is intended for dynamic SQL programs.

(2) A structure that describes input variables, output variables, or the columns of a result table.

SQL escape character

In DB2 UDB for OS/390, the symbol that is used to enclose an SQL delimited identifier. This symbol is the double quotation mark ("). Compare to escape character.

SQL ID

See SQL authorization ID.

SQL path

In DB2 UDB for OS/390, an ordered list of schema names that are used in the resolution of unqualified references to user-defined functions, distinct types, and stored procedures. In dynamic SQL, the current path is found in the CURRENT PATH special register. In static SQL, it is defined in the PATH bind option.

SQL processing conversation

Any conversation that requires access of DB2 UDB for OS/390 data, either through an application or by dynamic query requests.

SQL Processor Using File Input (SPUFI)

In DB2 UDB for OS/390, SQL Processor Using File Input. A facility of the TSO attachment subcomponent that enables the DB2I user to execute SQL statements without embedding them in an application program.

SQL return code

Either SQLCODE or SQLSTATE.

SQL routine

In DB2 UDB for OS/390, a user-defined function or stored procedure that is based on code that is written in SQL.

SQL string delimiter

In DB2 UDB for OS/390, a symbol that is used to enclose an SQL string constant. The SQL string delimiter is the apostrophe ('), except in COBOL applications, where the user assigns the symbol, which is either an apostrophe or a double quotation mark (").

SSCP

See system services control point.

SSI

In an OS/390 environment, subsystem interface.

SSM

In DB2 UDB for OS/390, subsystem member.

stack

An area in memory that stores temporary register information, parameters, and return addresses of subroutines.

staging table

In DB2 replication, a CCD table that can be used as the source for updating data to multiple target tables.

stand-alone

An attribute of a program that means it is capable of executing separately from DB2 UDB for OS/390, without using DB2 UDB for OS/390 services.

standard conflict detection

Conflict detection in which the Apply program searches for conflicts in rows that are already captured in the change data tables of the replica or user table. See also conflict detection, enhanced conflict detection, and row-replica conflict detection.

star schema

The type of relational database schema used by the OLAP Starter Kit, often created in the Data Warehouse Center.

statement

An instruction in a program or procedure.

statement handle

In CLI, a handle that refers to the data object that contains information about an SQL statement. This includes information such as dynamic arguments, bindings for dynamic arguments and columns, cursor information, result values, and status information. Each statement handle is associated with a connection handle.

statement string

For a dynamic SQL statement in a DB2 UDB for OS/390 environment, the character string form of the statement.

static bind

A process by which SQL statements are bound after they are precompiled. All static SQL statements are prepared for execution at the same time. See also bind.

statement trigger

In DB2 UDB for OS/390, a trigger that is defined with the trigger granularity FOR EACH STATEMENT.

static SQL

SQL statements that are embedded within a program, and are prepared during the program preparation process before the program is executed. After being prepared, a static SQL statement does not change, although values of host variables specified by the statement can change.

status

In the Data Warehouse Center, the work-in-progress processing condition of a step, such as scheduled, populating, or successful.

step

In the Data Warehouse Center, a single operation on data in a warehouse process. In most cases, a step includes a warehouse source, a description of the transformation or movement of data, and a target. A step can be run according to a schedule, or it can cascade from another step.

step edition

In the Data Warehouse Center, a snapshot of the data in a warehouse source at a particular time.

storage group

A named set of DASD volumes on which DB2 UDB for OS/390 data can be stored.

stored procedure

(1) A block of procedural constructs and embedded SQL statements that is stored in a database and can be called by name. Stored procedures allow an application program to be run in two parts. One part runs on the client and the other on the server. This allows one call to produce several accesses to the database. Synonym for procedure.

(2) In DB2 UDB for OS/390, a user-written application program that can be started through the use of the SQL CALL statement.

Stored Procedure Builder

A tool for creating stored procedures, building stored procedures on local and remote DB2 servers, modifying and rebuilding existing stored procedures, and testing and debugging the execution of installed stored procedures using a graphical interface. This tool is standalone or can be accessed from various integrated development environments.

Stored Procedure Builder project

A file that is created by the Stored Procedure Builder that contains connection information and stored procedure objects that have not been successfully built in the database.

storyboard

A visual summary of a video. The Video Extender includes features that can be used to identify and store video frames that are representative of the shots in a video. These representative frames can be used to build a storyboard.

string

In programming languages, the form of data used for storing and manipulating text.

strong typing

In DB2 UDB for OS/390, a process that guarantees that only user-defined functions and operations that are defined on a distinct type can be applied to that type. For example, you cannot directly compare two currency types, such as Canadian dollars and US dollars. But you can provide a user-defined function to convert one currency to the other and then do the comparison.

Structured Query Language (SQL)

A standardized language for defining and manipulating data in a relational database.

subagent

A type of agent that works on subrequests. A single application can make many requests, and each request can be broken into many subrequests. Therefore, there can be multiple subagents working on behalf of the same application. All subagents working for the application are coordinated by the coordinating agent for that application.

subcomponent

A group of closely related DB2 UDB for OS/390 modules that work together to provide a general function.

subject area

In the Data Warehouse Center, a set of processes that create warehouse data for a particular logical business area. Processes in a subject area operate on data for a particular subject to create the detail data, data summaries, and cubes needed by that subject.

subordinate agent

See subagent.

subpage

In DB2 UDB for OS/390, the unit into which a physical index page can be divided.

subquery

A SELECT statement within the WHERE or HAVING clause of another SQL statement; a nested SQL statement.

subscription

See subscription set.

subscription cycle

In DB2 replication, a process in which the Apply program retrieves changed data for a given subscription set, replicates the changes to the target table, and updates the appropriate replication control tables to reflect the progress it made.

subscription process

In DB2 replication, a process in which you define subscription sets and subscription-set members. Contrast with registration process.

subscription set

In DB2 replication, the specification of a group of source tables, target tables, and the control information that governs the replication of changed data. See also subscription-set member.

subscription-set member

In DB2 replication, a member of a subscription set. There is one member for each source-target pair. Each member defines the structure of the target table and which rows and columns will be replicated from the source table.

subselect

That form of a query that does not include an ORDER BY clause, an UPDATE clause, or UNION operators.

substitution character

In SQL, a unique character that is substituted during character conversion for any characters in the source program that do not have a match in the target coding representation.

subsystem

In DB2 UDB for OS/390, a distinct instance of a relational database management system (RDBMS).

symbolic destination name

Specifies the name of a remote partner. The name corresponds to an entry in the CPI Communications side information table that contains the necessary information (partner LU name, mode name, partner TP name) for the client to set up an APPC connection to the server.

synchronization level

In APPC, the specification indicating whether the corresponding transaction programs exchange confirmation requests and replies.

synchronous

Pertaining to two or more processes that depend upon the occurrences of specific events, such as a common timing signal. Contrast with asynchronous.

sync point

See point of consistency.

synonym

In DB2 UDB for OS/390, an alternative name, in SQL, for a table or view. Synonyms can only be used to refer to objects at the subsystem in which the synonym is defined.

syntactic character set

A set of 81 graphic characters that are registered in the IBM registry as character set 00640. This set was originally recommended to the programming language community to be used for syntactic purposes toward maximizing portability and interchangeability across systems and country boundaries. It is contained in most of the primary registered character sets, with a few exceptions. Compare to invariant character set.

Sysplex

See Parallel Sysplex.

Sysplex query parallelism

Parallel execution of a single query that is accomplished by using multiple tasks on more than one DB2 UDB for OS/390 subsystem. See also query CP parallelism.

system administrator

The person at a computer installation who designs, controls, and manages the use of the computer system.

system agent

A work request that DB2 UDB for OS/390 creates internally, such as prefetch processing, deferred writes, and service tasks.

system catalog

See catalog.

system conversation

The conversation that two DB2 UDB for OS/390 subsystems must establish to process system messages before any distributed processing can begin.

system database directory

A directory that contains entries for every database that can be accessed using the database manager. It is created when the first database is created or cataloged on the system.

system diagnostic work area (SDWA)

In an OS/390 environment, the data that is recorded in a SYS1.LOGREC entry that describes a program or hardware error.

system-managed space (SMS) table space

A table space whose space is managed by the operating system. This storage model is based on files created under subdirectories, and managed by the file system. Contrast with database managed space (DMS) table space.

system services control point (SSCP)

The control point in a SNA network that provides network services for dependent nodes.

Systems Network Architecture (SNA)

The description of the logical structure, formats, protocols, and operational sequences for transmitting information units through the networks and also the operational sequences for controlling the configuration and operation of networks.

SYS1.DUMPxx data set

In an OS/390 environment, a data set that contains a system dump.

SYS1.LOGREC

In an OS/390 environment, a service aid that contains important information about program and hardware errors.

T

table

A named data object consisting of a specific number of columns and some unordered rows. See also base table.

table check constraint

In DB2 UDB for OS/390, a user-defined constraint that specifies the values that specific columns of a base table can contain.

table designator

A column name qualifier that designates a specific object table.

table function

In DB2 UDB for OS/390, a function that receives a set of arguments and returns a table to the SQL statement that refers to the function. A table function can be referenced only in the FROM clause of a subselect.

table locator

In DB2 UDB for OS/390, a mechanism that allows access to trigger transition tables in the FROM clause of SELECT statements, the subselect of INSERT statements, or from within user-defined functions. A table locator is a fullword integer value that represents a transition table.

table queue

A mechanism for transferring rows between database nodes. Table queues are distributed row streams with simplified rules for the insertion and removal of rows. Table queues can also be used to deliver rows between different processes in the serial database.

table space

(1) An abstraction of a collection of containers into which database objects are stored. A table space provides a level of indirection between a database and the tables stored within the database. A table space:

Has space on media storage devices assigned to it.
Has tables created within it. These tables use space in the containers that belong to the table space. The data, index, long field, and LOB portions of a table can be stored in the same table space, or can be individually broken out into separate table spaces.

(2) In DB2 UDB for OS/390, a page set that is used to store the records in one or more tables.

table space container

A generic term describing an allocation of space to a table space. Depending on the table space type, the container can be a directory, device, or file.

table space set

In DB2 UDB for OS/390, a set of table spaces and partitions that should be recovered together for one of these reasons:

Each of them contains a table that is a parent or descendent of a table in one of the others.
The set contains a base table and associated auxiliary tables.

A table space set can contain both types of relationships.

target

In the Data Warehouse Center, a table, view, or file that is produced or populated by a step; the output of a step.

target server

In DB2 replication, the database location of the target table. Normally this is also the location of the Apply program.

target table

In DB2 replication, the table on the target server to which data is copied. It can be a user copy table, a point-in-time table, a base aggregate table, a change aggregate table, a consistent-change-data table, or a replica table.

task control block (TCB)

A control block that is used to communicate information about tasks within an address space that are connected to DB2 UDB for OS/390. An address space can support many task connections (as many as one per task), but only one address space connection.

TCB

See task control block.

TCP/IP

See Transmission Control Protocol/Internet Protocol.

TCP/IP port

A 2-byte value that identifies an end user or a TCP/IP network application within a TCP/IP host.

technical metadata

In the Data Warehouse Center, data that describes the technical aspects of the data, such as its database type and length. Technical metadata includes information about where the data comes from and the rules used to extract, clean, and transform the data. Much of the metadata in the Data Warehouse Center is technical metadata. Contrast with business metadata.

temporary table

A table created during the processing of an SQL statement to hold intermediate results. Contrast with result table.

temporary table space

A table space that can store only temporary tables.

territory

A portion of the POSIX locale that is mapped to the country code for internal processing by the database manager.

thread

(1) In some operating systems, the smallest unit of operation to be performed in a process.

(2) The DB2 UDB for OS/390 structure that describes an application's connection, traces its progress, processes resource functions, and delimits its accessibility to DB2 UDB for OS/390 resources and services. Most DB2 UDB for OS/390 functions execute under a thread structure. Compare to allied thread and database access thread.

three-part name

The full name of a table, view, or alias. It consists of a location name, authorization ID, and an object name, separated by periods.

threshold trigger

An event that occurs when the value of a performance variable exceeds or falls below a user-defined threshold value. The action that occurs as a result of a threshold trigger can be:

Logging information in an alert log file.
Displaying information in an alert log window.
Generating an audio alarm.
Issuing a message window.
Invoking a predefined command or program.

time

A three-part value that designates a time of day in hours, minutes, and seconds.

time duration

A DECIMAL(6,0) value that represents a number of hours, minutes, and seconds.

timeron

A unit of measurement used to give a rough relative estimate of the resources, or cost, required by the database server to execute two plans for the same query. The resources calculated in the estimate include weighted processor and I/O costs.

timeout

Abnormal termination of either the DB2 UDB for OS/390 subsystem or of an application because of the unavailability of resources. Installation specifications are set to determine both the amount of time DB2 UDB for OS/390 is to wait for IRLM services after starting, and the amount of time IRLM is to wait if a resource that an application requests is unavailable. If either of these time specifications is exceeded, a timeout is declared.

timestamp

A seven-part value that consists of a date and time expressed in years, months, days, hours, minutes, seconds, and microseconds.

timestamp duration

A DECIMAL(20,6) value that represents a number of years, months, days, hours, minutes, seconds, and microseconds.

Tivoli Storage Manager (TSM)

A client/server product that provides storage management and data access services in a heterogeneous environment. TSM supports various communication methods, provides administrative facilities to manage the backup and storage of files, and provides facilities for scheduling backup operations.

TM Database

See Transaction Manager Database.

TMP

In an OS/390 environment, Terminal Monitor Program.

to-do

A state of a unit of recovery that indicates that the changes by the unit of recovery to recoverable DB2 UDB for OS/390 resources are indoubt and must be either applied to the DASD media or backed out, as determined by the commit coordinator.

token

The basic syntactic unit of a computing language. A token consists of one or more characters, excluding the blank character and excluding characters within a string constant or delimited identifier.

topology and routing services (TRS)

An APPN control point component that manages the topology database and computes routes.

TP

See transaction program.

trace

A DB2 UDB for OS/390 facility that provides the ability to monitor and collect DB2 UDB for OS/390 monitoring, auditing, performance, accounting, statistics, and serviceability (global) data.

transaction

(1) An exchange between a workstation and a program, two workstations, or two programs that accomplish a particular action or result. An example is the entry of a customer's deposit and the update of the customer's balance. Synonym for unit of work.

(2) One Net.Data invocation. If persistent Net.Data is used, then a transaction can span multiple Net.Data invocations.

transaction compensation

A process that restores rows that are affected by a committed transaction that is rejected. When a committed transaction is rejected, the rows are restored to the state that they were in before the transaction was committed.

transaction lock

In DB2 UDB for OS/390, a lock that is used to control concurrent execution of SQL statements.

transaction manager

A function that assigns identifiers to transactions, monitors their progress, and takes responsibility for transaction completion and failure recovery.

Transaction Manager Database (TM Database)

A database that is used to log transactions when a two-phase commit (SYNCPOINT TWOPHASE) is used with DB2 databases. In the event of transaction failure, the TM Database information can be accessed to resynchronize databases involved in the failed transaction.

transaction program (TP)

An application program that uses APPC to communicate with a partner application program.

transaction program name

In SNA LU 6.2 conversations, the name of the program at the remote logical unit that is to be the other half of the conversation.

transformation

In the Data Warehouse Center, an operation performed on data. Pivot and cleanse are types of transformations.

transformer

A program that operates on warehouse data. The Data Warehouse Center provides two types of transformers: statistical transformers, which provide statistics about the data in one or more tables; and warehouse transformers, which prepare the data for analysis. Each step has a type that corresponds to the transformer used in a process that performs types of data manipulation. For example, a clean step uses the Clean transformer.

transition table

A named temporary table that contains the transition values for each row affected by the triggering modification. An old transition table contains the values of affected rows before the modification is applied, and a new transition table contains the values of the affected rows after the modification is applied.

transition variable

A variable that is valid only in FOR EACH ROW triggers. It allows access to the transition values for the current row. An old transition variable is the value of the row before the modification is applied, and the new transition variable is the value of the row after the modification is applied.

Transmission Control Protocol/Internet Protocol (TCP/IP)

A set of communications protocols that provide peer-to-peer connectivity functions for both local and wide area networks.

trigger

(1) In DB2, an object in a database that is invoked indirectly by the database manager when a particular SQL statement is run.

(2) A set of SQL statements that are stored in a DB2 UDB for OS/390 database and executed when a certain event occurs in a DB2 UDB for OS/390 table.

trigger activation

In DB2 UDB for OS/390, the process that occurs when the trigger event that is defined in a trigger definition is executed. Trigger activation consists of the evaluation of the triggered action condition and conditional execution of the triggered SQL statements.

trigger activation time

In DB2 UDB for OS/390, an indication in a trigger definition of whether the trigger should be activated before or after the triggered event.

trigger body

In DB2 UDB for OS/390, the set of SQL statements that is executed when a trigger is activated and its triggered action condition evaluates to true.

trigger cascading

In DB2 UDB for OS/390, the process that occurs when the triggered action of a trigger causes the activation of another trigger.

triggered action

(1) The action that is executed when the trigger event occurs.

(2) In DB2 UDB for OS/390, the SQL logic that is performed when a trigger is activated. The triggered action consists of an optional triggered action condition and a set of triggered SQL statements that are executed only if the condition evaluates to true.

triggered-action condition

(1) The search condition that controls the execution of the SQL statements within the triggered action.

(2) In DB2 UDB for OS/390, an optional part of the triggered action. This Boolean condition appears as a WHEN clause and specifies a condition that DB2 evaluates to determine if the triggered SQL statements should be executed.

triggered SQL statements

In DB2 UDB for OS/390, the set of SQL statements that is executed when a trigger is activated and its triggered action condition evaluates to true. Triggered SQL statements are also called the trigger body.

trigger event

In a trigger definition, an update operation (INSERT, UPDATE, or DELETE statement) that causes the trigger to be run.

trigger granularity

In DB2 UDB for OS/390, a characteristic of a trigger, which determines whether the trigger is activated:

Only once for the triggering SQL statement.
Once for each row that the SQL statement modifies.

trigger package

In DB2 UDB for OS/390, a package that is created when a CREATE TRIGGER statement is executed. The package is executed when the trigger is activated.

triggering event

In DB2 UDB for OS/390, the specified operation in a trigger definition that causes the activation of that trigger. The triggering event is comprised of a triggering operation (INSERT, UPDATE, or DELETE) and a triggering table on which the operation is performed.

triggering SQL operation

In DB2 UDB for OS/390, the SQL operation that causes a trigger to be activated when performed on the triggering table.

triggering table

In DB2 UDB for OS/390, the table for which a trigger is created. When the defined triggering event occurs on this table, the trigger is activated.

truncation

The process of discarding part of a result from an operation when it exceeds memory or storage capacity.

TSO

In an OS/390 environment, Time-Sharing Option.

TSO attachment facility

A DB2 UDB for OS/390 facility consisting of the DSN command processor and DB2I. Applications that are not written for the CICS or IMS environments can run under the TSO attachment facility.

tuning parameters table

A table at the source server that contains timing information used by the Capture program. The information includes:

How long to keep rows in the change data table.
How much time can elapse before changes are stored in a database log or journal.
How often to commit changed data to the unit of work tables.

two-phase commit

A two-step process by which recoverable resources and an external subsystem are committed. During the first step, the database manager subsystems are polled to ensure that they are ready to commit. If all subsystems respond positively, the database manager instructs them to commit.

typed parameter marker

A parameter marker that is specified along with its target data type. It has the general form:

CAST(? AS data-type)

type 1 indexes

Indexes that were created by a release of DB2 before DB2 for MVS/ESA Version 4 or that are specified as type 1 indexes in Version 4. Contrast with type 2 indexes. As of DB2 UDB for OS/390 Version 7, type 1 indexes are no longer supported.

type 2 indexes

Indexes that are created on a release of DB2 after DB2 for OS/390 Version 6 or that are specified as type 2 indexes in Version 4 or Version 6. Contrast with type 1 indexes.

U

UDF

See user-defined function.

UDT

See user-defined type.

unambiguous cursor

A cursor that allows a relational database to determine whether blocking can be used with the answer set. A cursor defined FOR FETCH ONLY or FOR READ ONLY can be used with blocking, whereas a cursor defined FOR UPDATE cannot.

unbind session (UNBIND)

A request to deactivate a session between two logical units (LUs).

uncommitted read (UR)

An isolation level that allows an application to access uncommitted changes of other transactions. The application does not lock other applications out of the row it is reading, unless the other application attempts to drop or alter the table.

uncoordinated transaction

A transaction that accesses more than one resource, but its commit or rollback is not being coordinated by a transaction manager.

underlying view

In DB2 UDB for OS/390, the view on which another view is directly or indirectly defined.

undo

A state of a unit of recovery that indicates that the changes that the unit of recovery made to recoverable DB2 UDB for OS/390 resources must be backed out.

Unicode

An international character encoding scheme that is a subset of the ISO 10646 standard. Each character supported is defined using a unique 2-byte code.

unique constraint

The rule that no two values in a primary key or key of a unique index can be the same. Also referred to as uniqueness constraint.

unique index

An index that ensures that no identical key values are stored in a table.

unique key

A key that is constrained so that no two of its values are equal.

unit of recovery

A recoverable sequence of operations within a single resource manager, such as an instance of DB2 UDB for OS/390. Contrast with unit of work.

unit of work

A recoverable sequence of operations within an application process. At any time, an application process is a single unit of work, but the life of an application process can involve many units of work as a result of commit or rollback operations. In a DB2 UDB for OS/390 multi-site update operation, a single unit of work can include several units of recovery. Synonym for transaction.

unit-of-work table

A replication control table at the source server that contains commit records read from the database log or journal. The records include a unit-of-recovery ID that can be used to join the unit-of-work table and the change data table to produce transaction-consistent change data. For DB2, the unit-of-work table optionally includes the correlation ID, which can be useful for auditing purposes.

unlock

The act of releasing an object or system resource that was previously locked and returning it to general availability within DB2 UDB for OS/390.

untyped parameter marker

A parameter marker that is specified without its target data type. It has the form of a single question mark.

update rule

A condition enforced by the database manager that must be met before a column can be updated.

update trigger

In DB2 UDB for OS/390, a trigger that is defined with the triggering SQL operation UPDATE.

upstream

In DB2 UDB for OS/390, the node in the syncpoint tree that is responsible, in addition to other recovery or resource managers, for coordinating the execution of a two-phase commit.

UR

See uncommitted read.

URE

In DB2 UDB for OS/390, unit of recovery element.

URID (unit of recovery ID)

In DB2 UDB for OS/390, the LOGRBA of the first log record for a unit of recovery. The URID also appears in all subsequent log records for that unit of recovery.

user copy table

In DB2 replication, a target table whose content matches all or part of a source table and contains only user data columns.

user-defined data type (UDT)

See distinct type.

user-defined distinct type

See distinct type.

user-defined function (UDF)

A function that is defined to the database management system and can be referred to in SQL queries. It can be one of the following functions:

An external function, in which the body of the function is written in a programming language whose arguments are scalar values and a scalar result is produced for each invocation.
A sourced function, implemented by another built-in or user-defined function already known to the DBMS. This function can be either a scalar function or column (aggregating) function, and returns a single value from a set of values (for example, MAX or AVG).

user-defined performance variable

A performance variable created by a user and added to the performance variable profile.

user-defined program

A program that a user supplies and defines to the Data Warehouse Center, as contrasted with supplied programs, which are included with and defined automatically in the Data Warehouse Center.

user-defined type (UDT)

A data type that is not native to the database manager and was created by a user. In DB2 UDB for OS/390, the term distinct type is used instead of user-defined type.

user mapping

An association between the authorization under which a user connects to a federated server and the authorization under which the user connects to a data source.

user table

In DB2 replication, a table created for and used by an application before it is defined as a replication source. It is used as the source for updates to read-only target tables, consistent-change-data tables, replicas, and row-replica tables.

UT

In DB2 UDB for OS/390, utility-only access.

UTC

See Coordinated Universal Time.

V

value

(1) The smallest unit of data manipulated in SQL.

(2) A specific data item at the intersection of a column and a row.

variable

A data element that specifies a value that can be changed.

variant function

A user-defined function whose result is dependent on its input parameter values as well as other factors. Successive invocations with the same parameter values might produce different results. Contrast with not-variant function.

varying-length string

A character, graphic, or binary string whose length is not fixed but can range within set limits. Also referred to as a variable-length string.

version

In DB2 UDB for OS/390, a member of a set of similar programs, DBRMs, packages, or LOBs.

A version of a program is the source code that is produced by precompiling the program. The program version is identified by the program name and a timestamp (consistency token).
A version of a DBRM is the DBRM that is produced by precompiling a program. The DBRM version is identified by the same program name and timestamp as a corresponding program version.
A version of a package is the result of binding a DBRM within a particular database system. The package version is identified by the same program name and consistency token as the DBRM.
A version of a LOB is a copy of a LOB value at a point in time. The version number for a LOB is stored in the auxiliary index entry for the LOB.

view

A logical table that consists of data that is generated by a query. Contrast with base table.

view check option

In DB2 UDB for OS/390, an option that specifies whether every row that is inserted or updated through a view must conform to the definition of that view. A view check option can be specified with the WITH CASCADED CHECK OPTION, WITH CHECK OPTION, or WITH LOCAL CHECK OPTION clauses of the CREATE VIEW statement.

Virtual Storage Access Method (VSAM)

An access method for direct or sequential processing of fixed-length and varying-length records on direct access devices. The records in a VSAM data set or file can be organized in logical sequence by a key field (key sequence), in the physical sequence in which they are written on the data set or file (entry-sequence), or by relative-record number.

Virtual Telecommunications Access Method (VTAM)

In an OS/390 environment, an IBM licensed program that controls communication and the flow of data in an SNA network.

Visual Explain

A tool that lets database administrators and application programmers use a graphical interface to display and analyze detailed information on the access plan of a given SQL statement. The tasks provided by this tool can be accessed from the Control Center.

VSAM

See Virtual Storage Access Method.

VTAM

See Virtual Telecommunication Access Method.

W

warehouse

A subject-oriented nonvolatile collection of data used to support strategic decision making. The warehouse is the central point of data integration for business intelligence. It is the source of data for datamarts within an enterprise and delivers a common view of enterprise data.

warehouse agent

In the Data Warehouse Center, a run-time process that manages data movement and transformation.

warehouse control database

The Data Warehouse Center database that contains the control tables that are required to store Data Warehouse Center metadata.

warehouse program group

In the Data Warehouse Center, a container (folder) that holds program objects.

warehouse source

A subset of tables and views from a single database, or a set of files, that have been defined to the Data Warehouse Center.

warehouse target

A subset of tables, indexes, and aliases from a single database that are managed by the Data Warehouse Center.

warm start

(1) A restart that allows reuse of previously initialized input and output work queues. Contrast with cold start.

(2) In DB2 replication, a start of the Capture program that allows reuse of previously initialized input and output work queues.

well known address

An address used to uniquely identify a particular node in the network to establish connections between nodes. The well known address is a combination of the network address and the port used on the logical node.

WLM application environment

An MVS Workload Manager attribute that is associated with one or more stored procedures. The WLM application environment determines the address space in which a given DB2 UDB for OS/390 stored procedure runs.

work file

In DB2 replication, a temporary file used by the Apply program when processing a subscription set.

wrapper

In a federated database system, the mechanism by which the federated server invokes routines to communicate with, and retrieve data from, a data source. The routines are contained in a library called a wrapper module.

write to operator (WTO)

An optional user-coded service that allows a message to be written to the system console operator informing the operator of errors and unusual system conditions that may need to be corrected.

WTO

See write to operator.

WTOR

A write to operator (WTO) with reply.

X

XCF

See cross-system coupling facility.

XID

Exchange station ID.

XRF

See extended recovery facility.

Appendix A. Using the DB2 Library

Partial Table-of-Contents

DB2 PDF Files and Printed Books

DB2 Information

Printing the PDF Books

Ordering the Printed Books

DB2 Online Documentation

Accessing Online Help

Viewing Information Online

Installing the Netscape Browser

Accessing Information with the Information Center

Using DB2 Wizards

Setting Up a Document Server

Searching Information Online

The DB2 Universal Database library consists of online help, books (PDF and HTML), and sample programs in HTML format. This section describes the information that is provided, and how you can access it.

To access product information online, you can use the Information Center. For more information, see Accessing Information with the Information Center. You can view task information, DB2 books, troubleshooting information, sample programs, and DB2 information on the Web.

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