DB2 UDB for OS/390 terms

A

abend
Abnormal end of task.

abend reason code
A 4-byte hexadecimal code that uniquely identifies a problem with DB2. A complete list of DB2 abend reason codes and their explanations is contained in DB2 for OS/390 Messages and Codes.

abnormal end of task (abend)
Termination of a task, a job, or a subsystem because of an error condition that cannot be resolved during execution by recovery facilities.

access method services
A utility program that defines and manages VSAM data sets (or files).

access path
The path used to get to data specified in SQL statements. An access path can involve an index or a sequential search.

active log
The portion of the DB2 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 those records that are older and no longer will fit on the active log.

active member state
A state of a member of a data sharing group. An active member is identified with a group by XCF, which associates the member with a particular task, address space, and MVS system. A member that is not active is failed or quiesced.

address space
A range of virtual storage pages identified by a number (ASID) and a collection of segment and page tables which map the virtual pages to real pages of the computer's memory.

address space connection
The result of connecting an allied address space to DB2. Each address space containing a task connected to DB2 has exactly one address space connection, even though more than one task control block (TCB) can be present. See allied address space and task control block.

after trigger
A trigger defined with the trigger activation time AFTER.

agent
As used in DB2, the structure that associates all processes involved in a DB2 work unit. An allied agent is generally synonymous with an allied thread. System agents are work units that process independently of the allied agent, such as prefetch processing, deferred writes, and service tasks.

alias
An alternate name that can be used in SQL statements to refer to a table or view in the same or a remote DB2 subsystem.

allied address space
An area of storage external to DB2 that is connected to DB2 and is therefore capable of requesting DB2 services.

allied thread
A thread originating at the local DB2 subsystem that may access data at a remote DB2 subsystem.

allocated cursor
A cursor defined for stored procedure results sets by using ALLOCATE CURSOR.

already verified
An LU 6.2 security option which allows DB2 to provide the user's verified authorization ID when allocating a conversation. The user is not validated by the partner DB2.

ambiguous cursor
A database cursor that is not defined with either the clauses FOR FETCH ONLY or FOR UPDATE OF, 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 SQL statements PREPARE or EXECUTE IMMEDIATE.

American National Standards Institute (ANSI)
An organization consisting of producers, consumers, and general interest groups, that establishes the procedures by which accredited organizations create and maintain voluntary industry standards in the United States.

ANSI
American National Standards Institute.

APAR
Authorized program analysis report.

APAR fix corrective service
A temporary correction of a DB2 defect. The correction is temporary because it is usually replaced at a later date by a more permanent correction such as a program temporary fix (PTF).

APF
Authorized program facility.

API
Application programming interface.

APPL
A VTAM network definition statement used to define DB2 to VTAM as an application program using SNA LU 6.2 protocols.

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

application plan
The control structure produced during the bind process and used by DB2 to process SQL statements encountered during statement execution.

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

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

application requester (AR)
See requester.

application server
See server.

AR
application requester. See requester.

archive log
The portion of the DB2 log that contains log records that have been copied from the active log.

AS
Application server. See server.

ASCII
An encoding scheme used to represent strings in many environments, typically on PCs and workstations. Contrast with EBCDIC.

attachment facility
An interface between DB2 and TSO, IMS, Customer Information Control System, or batch address spaces. An attachment facility allows application programs to access DB2.

attribute
A characteristic of an entity. For example, in database design, the phone number of an employee is one of that employee's attributes.

authorization ID
A string that can be verified for connection to DB2 and to which a set of privileges are allowed. It can represent an individual, an organizational group, or a function, but DB2 does not determine this representation.

authorized program analysis report (APAR)
A report of a problem caused by a suspected defect in a current release of a program.

authorized program facility (APF)
A facility that permits the identification of programs that are authorized to use restricted functions.

auxiliary index
An index on a auxiliary table in which each index entry refers to a LOB.

auxiliary table
A table that stores columns outside the table in which they are defined.



B

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

base table
(1) A table created by the SQL CREATE TABLE statement that is used to hold persistent data. Contrast with result table and temporary table.

(2) A table containing a LOB column definition. The actual LOB column data is not stored along with the base table. The base table contains a row identifier for each row and an indicator column for each of its LOB columns. Contrast with auxiliary table.

base table space
A table space that contains base tables.

basic predicate
A predicate that compares two values.

basic sequential access method (BSAM)
An access method for storing or retrieving data blocks in a continuous sequence, using either a sequential access or a direct access device.

before trigger
A trigger 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)
See BLOB.

binary string
A sequence of bytes that is not associated with a CCSID. The BLOB data type is a binary string.

bind
The process by which the output from the DB2 precompiler is converted to a usable control structure called a package or an application plan. During the process, access paths to the data are selected and some authorization checking is performed.

bit data
Data that is character type CHAR or VARCHAR and is not associated with a coded character set.

BLOB
A sequence of bytes, where the size of the sequence ranges from 0 bytes to 2 GB-1. Such a string does not have an associated CCSID. Although the size of binary large object values can be anywhere up to 2 GB-1, in general, they are used whenever a byte string might exceed the limits of the VARCHAR FOR BIT DATA type.

BMP
Batch Message Processing (IMS).

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

BSAM
Basic sequential access method.

BSDS
Bootstrap data set.

buffer pool
Main storage reserved to satisfy the buffering requirements for one or more table spaces or indexes.

built-in function
A function that is supplied by DB2. Contrast with user-defined function.



C

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

CAF
Call attachment facility.

call attachment facility (CAF)
A DB2 attachment facility for application programs running in TSO or MVS batch. The CAF is an alternative to the DSN command processor and allows greater control over the execution environment.

call level interface (CLI)
A callable application program interface (API) for database access, which is an alternative to using embedded SQL. In contrast to embedded SQL, DB2 CLI does not require the user to precompile or bind applications, but instead provides a standard set of functions to process SQL statements and related services at run time.

cascade delete
The enforcement of referential constraints by DB2 when it deletes all descendent rows of a deleted parent row.

CASE expression
Allows an expression to be selected based on the evaluation of one or more conditions.

cast function
A function used to convert instances of a (source) data type into instances of a different (target) data type. In general, a cast function has the name of the target data type. It has one single argument whose type is the source data type; its return type is the target data type.

castout
The DB2 process of writing changed pages from a group buffer pool to DASD.

catalog
In DB2, a collection of tables that contains descriptions of objects such as tables, views, and indexes.

catalog table
Any table in the DB2 catalog.

CCSID
Coded character set identifier.

CDB
See communications database.

CDRA
Character data representation architecture.

CEC
See central processor complex.

central electronic complex (CEC)
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
A declaration by an MVS administrator regarding the allocation rules for a coupling facility structure.

character data representation architecture (CDRA)
An architecture used to achieve consistent representation, processing, and interchange of string data.

character large object (CLOB)
See CLOB.

character set
A defined set of characters.

character string
A sequence of bytes representing bit data, single-byte characters, or a mixture of single and double-byte characters.

check clause
An extension to the SQL CREATE TABLE and SQL ALTER TABLE statements that specifies a table check constraint.

check constraint
See table check constraint.

check integrity
The condition that exists when each row in a table conforms to the table check constraints defined on that table. Maintaining check integrity requires enforcing table check constraints on operations that add or change data.

check pending
A state of a table space or partition that prevents its use by some utilities and some SQL statements, because it can contain rows that violate referential constraints, table check constraints, or both.

checkpoint
A point at which DB2 records internal status information on the DB2 log that would be used in the recovery process if DB2 should abend.

CI
Control interval.

Customer Information Control System
Represents (in this publication) Customer Information Control System/MVS and Customer Information Control System/ESA.

Customer Information Control System attachment facility
A DB2 subcomponent that uses the MVS Subsystem Interface (SSI) and cross storage linkage to process requests from Customer Information Control System to DB2 and to coordinate resource commitment.

CIDF
Control interval definition field.

claim
To register to DB2 that an object is being accessed. This registration is also called a claim. A claim is used to ensure that an object cannot be drained until a commit is reached. Contrast with drain.

claim class
A specific type of object access which can be one of the following:

claim count
A count of the number of agents that are accessing an object.

class of service
A VTAM term for a list of routes through a network, arranged in an order of preference for their use.

clause
In SQL, a distinct part of a statement, such as a SELECT clause or a WHERE clause.

CLI
See call level interface.

client
See requester.

CLIST
Command list. A language for performing TSO tasks.

CLOB
A sequence of bytes representing single-byte characters or a mixture of single and double-byte characters where the size can be up to 2 GB-1. Although the size of character large object values can be anywhere up to 2 GB-1, in general, they are used whenever a character string might exceed the limits of the VARCHAR type.

CLPA
Create link pack area.

clustering index
An index that determines how rows are physically ordered in a table space.

coded character set
A set of unambiguous rules that establish 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 16-bit number that uniquely identifies a coded representation of graphic characters. It designates an encoding scheme identifier and one or more pairs consisting of a character set identifier and an associated code page identifier.

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.

cold start
A process by which DB2 restarts without processing any log records. Contrast with warm start.

collection
A group of packages that have the same qualifier.

column
The vertical component of a table. A column has a name and a particular data type (for example, character, decimal, or integer).

column function
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 which defines a list of authorization IDs that are allowed to connect to DB2 from a partner LU.

command
A DB2 operator command or a DSN subcommand. Distinct from an SQL statement.

command prefix
A one- to eight-character command identifier. The command prefix distinguishes the command as belonging to an application or subsystem rather than MVS.

command recognition character (CRC)
A character that permits an MVS console operator or an IMS subsystem user to route DB2 commands to specific DB2 subsystems.

command scope
The scope of command operation in a data sharing group. If a command has member scope, the command displays information from the one member only or affects only non-shared resources owned locally by that member. If a command has group scope, the command displays information from all members, affects non-shared resources 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.

commit point
A point in time when data is considered consistent.

committed phase
The second phase of the multi-site update process that requests all participants to commit the effects of the logical unit of work.

common service area (CSA)
In MVS, a part of the common area that contains data areas addressable by all address spaces.

communications database (CDB)
A set of tables in the DB2 catalog that are used to establish conversations with remote database management systems.

comparison operator
A token (such as =, >, <) used to specify a relationship between two values.

composite key
An ordered set of key columns of the same table.

compression dictionary
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 more than one application process at the same time.

conditional restart
A DB2 restart that is directed by a user-defined conditional restart control record (CRCR).

connection
The existence of a communication path between two partner LUs that allows information to be exchanged (for example, two DB2s connected and communicating by way of a conversation).

connection ID
An identifier supplied by the attachment facility that is associated with a specific address space connection.

consistency token
A timestamp used to generate the version identifier for an application. See also version.

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 referential constraint, uniqueness constraint, and table check constraint.

control interval (CI)
A fixed-length area or 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 four bytes at the end of each control interval; it describes the free space, if any, in the control interval.

conversation
Advanced Program to Program Communication (APPC), or LU6.2, is a conversation between an application and a remote transaction program over an SNA logical unit - logical unit (LU-LU) session that allows communication while processing a transaction.

coordinator
The system component that coordinates the commit or rollback of a unit of work that includes work done on one or more other systems.

correlated columns
A relationship between the value of one column and the value of another column.

correlated subquery
A subquery (part of a WHERE or HAVING clause) applied to a row or group of rows of a table or view named in an outer sub-SELECT statement.

correlation ID
An identifier associated with a specific thread. In TSO, it is either an authorization ID or the job name.

correlation name
An identifier that designates a table, a view, or individual rows of 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 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:

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

coupling facility
A special PR/SM LPAR logical partition that runs the coupling facility control program and provides high-speed caching, list processing, and locking functions in a Sysplex.

CPC
See central processor complex.

CRC
Command recognition character.

CRCR
Conditional restart control record.

cross-memory linkage
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 MVS that provides functions to support cooperation between authorized programs running within a Sysplex.

CSA
Common service area.

current data
Data within a host structure that is current with (identical to) the data within the base table.

current status rebuild
The second phase of restart processing during which the status of the subsystem is reconstructed from information on the log.

cursor
A named control structure used by an application program to point to a row of interest within some set of rows, and to retrieve rows from the set, possibly making updates or deletions.

cursor stability (CS)
The isolation level that provides maximum concurrency without the ability to read uncommitted data. With cursor stability, a unit of work holds locks only on its uncommitted changes and on the current row of each of its cursors.

cursor table (CT)
The cursor table is the copy of the skeleton cursor table used by an executing application process.

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



D

DASD
Direct access storage device.

database
A collection of tables, or a collection of table spaces and index spaces.

database access thread
A thread accessing data at the local subsystem on behalf of a remote subsystem.

database administrator (DBA)
An individual responsible for the design, development, operation, safeguarding, maintenance, and use of a database.

database descriptor (DBD)
An internal representation of DB2 database definition which reflects the data definition found in the DB2 catalog. The objects defined in a database descriptor are table spaces, tables, indexes, index spaces, and relationships.

database management system (DBMS)
A software system that controls the creation, organization, and modification of a database and access to the data stored within it.

database request module (DBRM)
A data set member created by the DB2 precompiler that contains information about SQL statements. DBRMs are used in the bind process.

DATABASE 2 Interactive (DB2I)
The DB2 facility that provides for the execution of SQL statements, DB2 (operator) commands, programmer commands, and utility invocation.

data currency
The state in which data retrieved into a host variable in your program is a copy of data in the base table.

data definition name (DD name)
The name of a data definition (DD) statement that corresponds to a data control block containing the same name.

Data Language/I (DL/I)
The IMS data manipulation language; a common high-level interface between a user application and IMS.

data partition
A VSAM data set that is contained within a partitioned table space.

data sharing
The ability of two or more DB2 subsystems to directly access and change a single set of data.

data sharing group
A collection of one or more DB2 subsystems that directly access and change the same data while maintaining data integrity.

data sharing member
A DB2 subsystem assigned by XCF services to a data sharing group.

data space
A range of up to 2GB 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 or system data or programs.

data type
An attribute of columns, literals, host variables, special registers, and the results of functions and expressions.

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

date duration
A decimal integer that represents a number of years, months, and days.

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

DBA
Database administrator.

DBCLOB
A sequence of bytes representing double-byte characters where the size can be up to 2 gigabytes. Although the size of double-byte character large object values can be anywhere up to 2 gigabytes, in general, they are used whenever a double-byte character string might exceed the limits of the VARGRAPHIC type.

DBCS
Double-byte character set.

DBD
Database descriptor.

DBID
Database identifier.

DBMS
Database management system.

DBRM
Database request module.

DB2 catalog
Tables maintained by DB2 that contain descriptions of DB2 objects such as tables, views, and indexes.

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

DB2I
DATABASE 2 Interactive.

DB2I Kanji Feature
The tape that contains the panels and jobs that allow a site to display DB2I panels in Kanji.

DB2 PM
DATABASE 2 Performance Monitor.

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

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

DCE
See Distributed Computing Environment.

DCLGEN
Declarations generator.

DDF
Distributed data facility.

DD name
Data definition name.

deadlock
Unresolvable contention for the use of a resource such as a table or an index.

declarations generator (DCLGEN)
A subcomponent of DB2 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 system catalog information. DCLGEN is also a DSN subcommand.

default value
A predetermined value, attribute, or option that is assumed when no other is explicitly specified.

deferred embedded SQL
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.

degree of parallelism
The number of concurrently executed operations that are initiated to process a query.

delete-connected
A table is delete-connected to table P if it is a dependent of P or a dependent of a table to which delete operations from P cascade.

delete rule
The rule that tells DB2 what to do to a dependent row when a parent row is deleted. For each relationship, the rule might be CASCADE, RESTRICT, SET NULL, or NO ACTION.

delete trigger
A trigger defined with the triggering SQL operation DELETE.

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

dependent
An object (row, table, or table space) is a dependent if it has at least one parent. The object is also said to be a dependent (row, table, or table space) of its parent. See parent row, parent table, parent table space.

dependent row
A row that contains a foreign key that matches the value of a primary key in the parent row.

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

descendent
An object is a descendent of another object if it is a dependent of the object, or if it is the dependent of a descendent of that object.

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

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

deterministic function
A user-defined function whose result is dependent on the values of the input arguments. That is, successive invocations with the same argument values produce the same answer. Sometimes referred to as a not-variant function. Contrast this with an not-deterministic function (sometimes called a variant function) which might not always produce the same result for the same inputs.

DFHSM
Data Facility Hierarchical Storage Manager.

DFP
Data Facility Product (MVS).

direct access storage device (DASD)
A device in which access time is independent of the location of the data.

directory
The system database that contains internal objects such as database descriptors and skeleton cursor tables.

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 MVS/ESA (DCE MVS/ESA)
A set of technologies provided by the Open Software Foundation to implement distributed computing.

distributed data facility (DDF)
A set of DB2 components through which DB2 communicates with another RDBMS.

distributed relational database architecture (DRDA)
A connection protocol for distributed relational database processing that is used by IBM's relational database products. DRDA includes protocols for communication between an application and a remote relational database management system, and for communication between relational database management systems.

DL/I
Data Language/I. The IMS data manipulation language; a common high-level interface between a user application and IMS.

domain name
The name used by TCP/IP applications to refer to a TCP/IP host within a TCP/IP network.

domain name server (DNS)
A special TCP/IP network server that manages a distributed directory that is used to map TCP/IP host names to IP addresses.

double-byte character large object (DBCLOB)
See DBCLOB.

double-byte character set (DBCS)
A set of characters used by national languages such as Japanese and Chinese that have more symbols than can be represented by a single byte. Each character is two bytes in length, and therefore requires special hardware to be displayed or printed.

double-precision floating point number
A 64-bit approximate representation of a real number.

drain
To acquire a locked resource by quiescing access to that object.

drain lock
A lock on a claim class which prevents a claim from occurring.

DRDA
Distributed relational database architecture.

DRDA access
A method of accessing distributed data by which you can connect to another location, using an SQL statement, to execute packages that have been 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 DB2 private protocol access.

DSN
(1) The default DB2 subsystem name.
(2) The name of the TSO command processor of DB2.
(3) The first three characters of DB2 module and macro names.

duration
A number that represents an interval of time. See date duration, labeled duration, and time duration.

dynamic SQL
SQL statements that are prepared and executed within an application program while the program is executing. In dynamic SQL, the SQL source is contained in host language variables rather than being coded into the application program. The SQL statement can change several times during the application program's execution.



E

EBCDIC
Extended binary coded decimal interchange code. An encoding scheme used to represent character data in the MVS, VM, VSE, and OS/400 environments. Contrast with ASCII.

EDM pool
A pool of main storage 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.

enclave
In Language Environment for MVS & VM, 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 (ASCII or EBCDIC).

EOM
End of memory.

EOT
End of task.

error page range
Range of pages considered to be physically damaged. DB2 will not allow a user to access any pages that fall within this range.

equi-join
A join operation in which the join-condition has the form expression = expression.

escape character
The symbol used to enclose an SQL delimited identifier. The escape character is the quotation mark ("), except in COBOL applications, where the symbol (either a quotation mark or an apostrophe) can be assigned by the user.

ESDS
Entry sequenced data set.

ESMT
External subsystem module table (IMS).

EUR
IBM European Standards.

exception table
A table that holds rows that violate referential constraints or table check constraints found by the CHECK DATA utility.

exclusive lock
A lock that prevents concurrently executing application processes from reading or changing data. Contrast with shared lock.

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

exit routine
A user-written (or IBM-provided default) program that receives control from DB2 to perform specific functions. Exit routines run as extensions of DB2.

explicit hierarchical locking
Locking used to make the parent/child relationship between resources known to IRLM. This is done to avoid global locking overhead when no inter-DB2 interest exists on a resource.

exposed name
Names specified in a FROM clause are exposed or non-exposed. An exposed name is a correlation name or a table or view name for which a correlation name is not specified.

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

external function
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
A user-defined function or stored procedure based on code written in an external programming language.



F

failed member state
A state of a member of a data sharing group. A failed member has permanent status recording with XCF, and its task, address space, or MVS system has terminated before the state changed from active to quiesced.

fallback
The process of returning to a previous release of DB2 after attempting or completing migration to a current release.

false global lock contention
A contention indication from the coupling facility when multiple lock names are hashed to the same indicator and when there is no real contention.

field procedure
A user-written exit routine designed to receive a single value and transform (encode or decode) it in any way the user can specify.

file reference variable
A host variable used to indicate that data resides in a file rather than a memory buffer. This variable is used to retrieve a large object (directly to a file) or to insert a large object into a table (directly from a file). (DB2 for MVS/ESA does not directly support file reference variables.)

filter factor
A number between zero and one that estimates the proportion of rows in a table for which a predicate is true.

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

foreign key
A key that is specified in the definition of a referential constraint. Because of the foreign key, the table is a dependent table. The key must have the same number of columns, with the same descriptions, as the primary key of the parent table.

forward log recovery
The third phase of restart processing during which DB2 processes the log in a forward direction to apply all REDO log records.

free space
The total unused space in a page, that is, the space not used to store records or control information.

full outer join
The result of a join operation that includes the matched rows of both tables being joined and preserves the unmatched rows of both tables. See also join.

function
A specific purpose of an entity or its characteristic action such as a column function or scalar function. (See column function and scalar function.)

Furthermore, functions can be user-defined, built-in, or generated by DB2. (See built-in function, cast function, user-defined function, external function, sourced function.)

function definer
The authorization ID of the owner of the schema of the function specified in the CREATE FUNCTION statement.

function implementer
The authorization ID of the owner of the function program and function package.

function package
A package that results from binding the DBRM for a function program.

function package owner
The authorization ID of the user who binds the function program's DBRM into a function package.

function resolution
The process, internal to the DBMS, by which a function invocation is bound to a particular function instance. This process uses the function name, the data types of the arguments, and a list of the applicable schema names (called the SQL path) to make the selection. This process is sometimes called function selection.

function selection
See function resolution.

function signature
The logical concatenation of a fully qualified function name with the data types of all of its parameters.



G

GB
Gigabyte (1,073,741,824 bytes).

GBP-dependent
A page set or page set partition status when it is dependent upon the group buffer pool. There is either inter-DB2 read/write interest active for this page set or the page set has changed pages in the group buffer pool that have not yet been castout to DASD.

generalized trace facility (GTF)
An MVS service program that records significant system events such as I/O interrupts, SVC interrupts, program interrupts, or external interrupts.

generic resource name
A name used by VTAM that represents several application programs that provide the same function in order to handle session distribution and balancing in a Sysplex.

getpage
An operation in which DB2 accesses a data page.

GIMSMP
The load module name for the System Modification Program/Extended, a basic tool for installing, changing, and controlling changes to programming systems.

global lock
A lock that provides both intra-DB2 concurrency control and inter-DB2 concurrency control, that is, the scope of the lock is across all the DB2s of a data sharing group.

global lock contention
Conflicts on locking requests between different DB2 members of a data sharing group regarding attempts to serialize shared resources.

governor
See resource limit facility.

graphic string
A sequence of DBCS characters.

gross lock
The shared, update, or exclusive mode locks on a table, partition, or table space.

group buffer pool
A coupling facility cache structure used by a data sharing group to cache data and to ensure that the data is consistent for all members.

group buffer pool duplexing
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
The MVS XCF identifier for a data sharing group.

group restart
A restart of at least one member of a data sharing group after either locks or the shared communications area have been lost.

GTF
Generalized trace facility.



H

hiperspace
A range of up to 2GB 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 is not directly addressable. To manipulate data in a hiperspace, you bring the data into the address space in 4KB blocks.

home address space
The area of storage that MVS currently recognizes as "dispatched".

host
The set of programs and resources that are available on a given TCP/IP instance.

host identifier
A name declared in the host program.

host language
A programming language in which you can embed SQL statements.

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

host structure
In an application program, a structure referenced by embedded SQL statements.

host variable
In an application program, an application variable referenced by embedded SQL statements.

HSM
Hierarchical storage manager.



I

ICF
Integrated catalog facility.

IDCAMS
An IBM program used to process access method services (AMS) commands. It can be invoked as a job or jobstep, from a TSO terminal, or from within a user's application program.

IDCAMS LISTCAT
A facility for obtaining information contained in the access method services catalog.

identify
A request that an attachment service program in an address space separate from DB2 issues via the MVS subsystem interface to inform DB2 of its existence and initiate the process of becoming connected to DB2.

IFCID
Instrumentation facility component identifier.

IFI
Instrumentation facility interface.

IFI call
An invocation of the instrumentation facility interface (IFI) by means of one of its defined functions.

IFP
IMS Fast Path.

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

IMS
Information Management System.

IMS attachment facility
A DB2 subcomponent that uses MVS Subsystem Interface (SSI) protocols and cross-memory linkage to process requests from IMS to DB2 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 fails after a unit of recovery begins to be rolled back, but before the process is completed, DB2 will continue to back out the changes during restart.

in-commit
A status of a unit of recovery. If DB2 fails after beginning its phase 2 commit processing, it "knows", when restarted, that changes made to data are consistent. Such units of recovery are termed in-commit.

independent
An object (row, table, or table space) is independent if it is neither a parent nor a dependent of another object.

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

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

index partition
A VSAM data set that is contained within a partitioned index space.

index space
A page set used to store the entries of one index.

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.

indicator column
A 4-byte value stored in a base table in place of a LOB column.

indoubt
A status of a unit of recovery. If DB2 fails after it has finished its phase 1 commit processing and before it has started phase 2, only the commit coordinator knows if this unit of recovery is to be committed or rolled back. At emergency restart, if DB2 does not have the information needed to make this decision, its unit of recovery is indoubt until DB2 obtains this information from the coordinator.

indoubt resolution
The process of resolving the status of an indoubt logical unit of work to either the committed or the rollback state.

inflight
A status of a unit of recovery. If DB2 fails before its unit of recovery completes phase 1 of the commit process, it merely backs out the updates of its unit of recovery when it is restarted. These units of recovery are termed inflight.

inheritance
The ability of one object to pass its attributes to another object.

inline copy
A copy produced by the LOAD or REORG utility. The data set produced by the inline copy is logically equivalent to a full image copy produced by running the COPY utility with read-only access (SHRLEVEL REF).

inner join
The result of a join operation that includes only the matched rows of both tables being joined. See also join.

inoperative package
A package that cannot be used because one or more user-defined functions that the package depends on were dropped. Such a package must be explicitly rebound. Contrast with invalid package.

insert trigger
A trigger defined with the triggering SQL operation INSERT.

install
The process of preparing a DB2 subsystem to operate as an MVS subsystem.

installation verification scenario
A sequence of operations that exercises the main DB2 functions and tests whether DB2 was correctly installed.

instrumentation facility component identifier (IFCID)
Names a traceable event and identifies the trace record of that event. As a parameter on the -START TRACE and -MODIFY TRACE commands, it specifies tracing the corresponding event.

Interactive System Productivity Facility (ISPF)
An IBM licensed program that provides interactive dialog services.

internal resource lock manager (IRLM)
An MVS subsystem used by DB2 to control communication and database locking.

inter-DB2 R/W interest
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.

invalid package
A package becomes invalid when the package depends on an object ,other than a user-defined function, that is dropped. Such a package is implicitly rebound upon invocation. Contrast with inoperative package.

invariant character set

  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.

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

IRLM
internal resource lock manager.

ISO
International Standards Organization.

isolation level
The degree to which a unit of work is isolated from the updating operations of other units of work. See also cursor stability, repeatable read, uncommitted read, and read stability.

ISPF
Interactive System Productivity Facility.

ISPF/PDF
Interactive System Productivity Facility/Program Development Facility.



J

JCL
Job control language.

JES
MVS Job Entry Subsystem.

JIS
Japanese Industrial Standard.

join
A relational operation that allows retrieval of data from two or more tables based on matching column values. See also full outer join, inner join, left outer join, outer join, right outer join, equi-join.



K

KB
Kilobyte (1024 bytes).

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

keyword
In SQL, a name that identifies an option used in an SQL statement.

KSDS
Key sequenced data set.



L

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

large object (LOB)
See LOB.

large partitioned table space
A table space that allows the partitioned table it contains to exceed 64 GB of data in either compressed or uncompressed format.

latch
A DB2 internal mechanism for controlling concurrent events or the use of system resources.

LCID
Log control interval definition.

LDS
Linear data set.

leaf page
A page that contains pairs of keys and RIDs and that points to actual data. Contrast with nonleaf page.

left outer join
The result of a join operation that includes the matched rows of both tables being joined, and preserves the unmatched rows of the first table. See also join.

linear data set (LDS)
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.

link-edit
To create a loadable computer program using a linkage editor.

L-lock
See logical lock.

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

LOB
A sequence of bytes representing bit data, single-byte characters, double-byte characters, or a mixture of single and double-byte characters. A LOB can be up to 2GB -1 bytes in length. See also BLOB, CLOB, and DBCLOB.

LOB locator
A mechanism that allows an application program to manipulate a large object value in the database system. A LOB locator is a fullword integer value that represents a single LOB value. An application program retrieves a LOB locator into a host variable; it can then apply SQL functions to the associated LOB value using the locator.

LOB lock
A lock on a LOB value.

LOB table space
Analogous to table space, a LOB table space contains all the data for a particular LOB column in the related base table.

local
Refers to any object maintained by the local DB2 subsystem. A local table, for example, is a table maintained by the local DB2 subsystem. Contrast with remote.

local lock
A lock that provides intra-DB2 concurrency control, but does not provide inter-DB2 concurrency control; that is, its scope is a single DB2.

local subsystem
The unique RDBMS to which the user or application program is directly connected (in the case of DB2, by one of the DB2 attachment facilities).

location name
The name by which DB2 refers to a particular DB2 subsystem in a network of subsystems. Contrast with LU name.

lock
A means of controlling concurrent events or access to data. DB2 locking is performed by the IRLM.

lock duration
The interval over which a DB2 lock is held.

lock escalation
The promotion of a lock from a row, page, or LOB lock to a table space lock because the number of page locks concurrently held on a given resource exceeds a preset limit.

locking
The process by which the integrity of data is ensured. Locking prevents concurrent users from accessing inconsistent data.

lock mode
A representation for the type of access concurrently running programs can have to a resource held by a DB2 lock.

lock object
The resource that is controlled by a DB2 lock.

lock parent
For explicit hierarchical locking, a lock 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 lock to a higher level.

lock size
The amount of data controlled by a DB2 lock on table data; the value can be a row, a page, a LOB, a partition, a table, or a table space.

lock structure
A coupling facility data structure composed of a series of lock entries to support shared and exclusive locking for logical resources.

log
A collection of records that describe the events that occur during DB2 execution and their sequence. The information thus recorded is used for recovery in the event of a failure during DB2 execution.

logical claim
A claim on a logical partition of a nonpartitioned index.

logical drain
A drain on a logical partition of a nonpartitioned index.

logical index partition
The set of all keys that reference the same data partition.

logical lock
The lock type used by transactions to control intra- and inter-DB2 data concurrency between transactions.

logically complete
The concurrent copy process is finished with the initialization of the target objects being copied. The target objects are available for update.

logical page list (LPL)
A list of pages in error that cannot be referenced by applications until the pages are recovered. The page is in 'logical error' because there may be nothing wrong with the media (coupling facility or DASD) itself. Usually a connection to the media has been lost.

logical partition
A set of key/RID pairs in a nonpartitioned index that are associated with a particular partition.

logical recovery pending (LRECP)
The state in which the data and the index keys that reference the data are inconsistent.

logical unit
An access point through which an application program accesses the SNA network in order to communicate with another application program.

logical unit of work (LUW)
In IMS, the processing that program performs between synchronization points.

logical unit of work identifier (LUWID)
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 attempts to locate the current end of the log.

log record sequence number (LRSN)
A number DB2 generates and associates with each log record. DB2 also uses the LRSN for page versioning. The LRSNs generated by a given DB2 data sharing group form a strictly increasing sequence for each DB2 log and a strictly increasing sequence for each page across the DB2 group.

log truncation
A process by which an explicit starting RBA is established. This RBA is the point at which the next byte of log data will be written.

long string
A string whose actual length, or a varying-length string whose maximum length, is greater than 254 bytes or 127 double-byte characters. Any LOB column is a long string.

LPL
See logical page list.

LRECP
Logical recovery pending.

LRH
Log record header.

LRSN
See log record sequence number.

LU name
From logical unit name, the name by which VTAM refers to a node in a network. Contrast with location name.

LUW
Logical unit of work.

LUWID
Logical unit of work identifier.



M

mapping table
A table used by the REORG utility to map between the RIDs of data records in the original copy and the shadow copy. This table is created by the user.

materialize
(1) The process of putting rows from a view or nested table expression into a work file for further processing by a query.

(2) To place a LOB value into contiguous storage. Since LOB values can be very large, DB2 avoids materializing LOB data until it becomes absolutely necessary.

MB
Megabyte (1,048,576 bytes).

member name
The MVS XCF identifier for a particular DB2 subsystem in a data sharing group.

menu
A displayed list of available functions for selection by the operator. Sometimes called a menu panel.

migration
The process of converting a DB2 subsystem with a previous release of DB2 to an updated or current release. In this process, you can acquire the functions of the updated or current release without losing the data you created on the previous release.

mixed data string
A character string that can contain both single-byte and double-byte characters.

MLPA
Modified link pack area.

MODEENT
A VTAM macro instruction which associates a logon mode name with a set of parameters representing session protocols. A set of MODEENT macro instructions defines a logon mode table.

mode name
A VTAM name for the collection of physical and logical characteristics and attributes of a session.

modify locks
An L-lock or P-lock that has been specifically requested as having the MODIFY attribute. A list of these active locks are kept at all times in the coupling facility lock structure. If the requesting DB2 fails, that DB2's modify locks are converted to retained locks.

MPP
Message processing program (IMS).

MSS
Mass Storage Subsystem

MTO
Master terminal operator.

multi-site update
Distributed relational database processing in which data is updated in more than one location within a single unit of work.

must-complete
A state during DB2 processing in which the entire operation must be completed to maintain data integrity.

MVS
Multiple Virtual Storage.

MVS/ESA
Multiple Virtual Storage/Enterprise Systems Architecture.

MVS/XA
Multiple Virtual Storage/Extended Architecture.



N

negotiable lock
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
A subselect in a FROM clause (surrounded by parentheses).

NID (network identifier)
The network ID assigned by IMS or CICS, or if the connection type is RRSAF, the OS/390 RRS Unit of Recovery ID (URID).

nonleaf page
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.

nonpartitioned index
Any index that is not the partitioned index of a partitioned table space.

not-deterministic function
A user-defined function whose result is not solely dependent on the values of the input arguments. That is, successive invocations with the same argument values can produce a different answer. Sometimes referred to as a variant function. Contrast this with a deterministic function (sometimes called a not-variant function) which always produces the same result for the same inputs.

not-variant function
See deterministic function.

NRE
Network recovery element.

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

null
A special value that indicates the absence of information.

NULLIF
A scalar function which evaluates two passed expressions, returning NULL if the arguments are equal, or the value of the first argument if they are not.

NUL-terminated host variable
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, 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 IMS, a 4-byte number assigned sequentially to each IMS schedule since the last cold start of IMS and used as an identifier for a unit of work. In an 8-byte format, the first four bytes contain the schedule number and the last four 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
Data object identifier.

ordinary identifier
An uppercase letter followed by zero or more characters, each of which is an uppercase letter, a digit, 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 a parallel group, the primary agent that receives data from other execution units (referred to as parallel tasks) that are executing portions of the query in parallel.

outer join
The result of a join operation that includes the matched rows of both tables being joined and preserves some or all of the unmatched rows of the tables being joined. See also join.

overloaded function
A function name for which there are multiple function instances.



P

package
Also application package. An object containing a set of SQL statements that have been bound statically and that are available for processing.

package list
An ordered list of package names that may be used to extend an application plan.

package name
The name given an object 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.

page
A unit of storage within a table space (4KB, 8KB, 16KB, or 32KB) or index space (4KB). In a table space, a page contains one or more rows of a table. In a LOB table space, a LOB value can span more than one page but no more than one LOB value is stored on a page.

page set
Another way to refer to a table space or index space. Each page set is made from a collection of VSAM data sets.

page set recovery pending (PSRCP)
A restrictive state of an index space in which the page set is in a recovery pending state. In this case, the entire page set must be recovered. Recovery of a logical part is prohibited.

panel
A predefined display image that defines the locations and characteristics of display fields on a display surface (for example, a menu panel).

parallel group
A set of consecutive operations executed in parallel that have the same number of parallel tasks.

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

parallel task
The execution unit that is dynamically created to process a query in parallel. It is implemented by an MVS service request block.

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 could appear if the statement string was a static SQL statement.

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

parent row
A row whose primary key value is the foreign key value of a dependent row.

parent table
A table whose primary key is referenced by the foreign key of a dependent table.

parent table space
A table space that contains a parent table. A table space containing a dependent of that table is a dependent table space.

participant
An entity other than the commit coordinator that takes part in the commit process. Synonymous with agent in SNA.

partition
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 gigabytes, depending upon the number of partitions in the partitioned page set. All partitions of a given page set have the same maximum size.

partitioned data set (PDS)
A data set in direct access storage that is divided into partitions, called members, each of which can contain a program, part of a program, or data. Synonymous with program library.

partitioned page set
A partitioned table space or an index space. Header pages, space map pages, data pages, and index pages reference data only within the scope of the partition.

partitioned table space
A table space subdivided into parts (based upon index key range), each of which may be processed by utilities independently.

partner logical unit
An access point in the SNA network that is connected to the local DB2 by way of a VTAM conversation.

path
See current path.

PCT
Program control table (Customer Information Control System).

PDS
Partitioned data set.

piece
A data set of a nonpartitioned page set.

physical claim
A claim on an entire nonpartitioned index.

physical consistency
The state of a page that is not in a partially changed state.

physical drain
A drain on an entire nonpartitioned index.

physical lock contention
Conflicting states of the requesters for a physical lock. See negotiable lock.

physical lock (P-lock)
A lock type used only by data sharing that is acquired by DB2 to provide consistency of data cached in different DB2 subsystems.

physically complete
The concurrent copy process is completed and the output data set has been created.

plan
See application plan.

plan allocation
The process of allocating DB2 resources to a plan in preparation to execute it.

plan name
The name of an application plan.

plan segmentation
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
Program list table (Customer Information Control System).

point of consistency
A time when all recoverable data an application accesses is consistent with other data. Synonymous with sync point or commit point.

policy
See CFRM policy.

postponed abort UR
A UR that was inflight or in-abort, was interrupted by system failure or cancellation, and did not complete backout during restart.

PPT
(1) Processing program table (Customer Information Control System).
(2) Program properties table (MVS).

precision
In SQL, the total number of digits in a decimal number (called the size in the C language). In the C language, the number of digits to the right of the decimal point (called the scale in SQL). The DB2 library uses the SQL definitions.

precompilation
A processing of application programs containing SQL statements that takes place before compilation. SQL statements are replaced with statements that are recognized by the host language compiler. Output from this precompilation includes source code that can be submitted to the compiler and the database request module (DBRM) that is input to the bind process.

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

prefix
A code at the beginning of a message or record.

prepare
The first phase of a two-phase commit process in which all participants are requested to prepare for commit.

prepared SQL statement
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.

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

primary index
An index that enforces the uniqueness of a primary key.

primary key
A unique, nonnull key that is part of the definition of a table. A table cannot be defined as a parent unless it has a unique key or primary key.

principal
An entity that can communicate securely with another entity. In the Distributed Computing Environment, principals are represented as entries in the DCE registry database and include users, servers, computers, and others.

principal name
The name by which a principal is known to the DCE security services.

private connection
A communications connection that is specific to DB2.

privilege
The capability of performing a specific function, sometimes on a specific object. The term includes:

privilege set
For the installation SYSADM ID, the set of all possible privileges. For any other authorization ID, the set of all privileges recorded for that ID in the DB2 catalog.

process
A general term for a unit that depends on the environment, but has the same basic properties in every environment. A process involves the execution of one or more programs, and is the unit to which resources and locks are allocated. The execution of an SQL statement is always associated with some process.

program
A single compilable collection of executable statements in a programming language.

program temporary fix (PTF)
A solution or bypass of a problem diagnosed as a result of a defect in a current unaltered release of a licensed program. An authorized program analysis report (APAR) fix is corrective service for an existing problem. A PTF is preventive service for problems that might be encountered by other users of the product. A PTF is "temporary" because a permanent fix is usually not incorporated into the product until its next release.

protected conversation
A VTAM conversation that supports two-phase commit flows.

PSRCP
Page set recovery pending.

PTF
Program temporary fix.



Q

QMF
Query Management Facility.

QSAM
Queued Sequential Access Method.

query
A component of certain SQL statements that specifies a result table.

query block
The part of a query represented by one of the FROM clauses. There can be multiple query blocks per FROM clause, depending on DB2's internal processing of the query.

query CP parallelism
Parallel execution of a single query accomplished by using multiple tasks. See also Sysplex query parallelism.

query I/O parallelism
Parallel access of data accomplished by triggering multiple I/O requests within a single query.

quiesced member state
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's task, address space, or MVS system fails before the command takes effect, the member state is failed.



R

RACF
OS/VS2 MVS Resource Access Control Facility.

RBA
Relative byte address.

RCT
Resource control table (Customer Information Control System attachment facility).

RDB
See relational database.

RDBMS
Relational database management system.

RDBNAM
See relational database name.

RDF
Record definition field.

read stability (RS)
An isolation level that is similar to repeatable read but does not completely isolate an application process from all other concurrently executing application processes. Under level RS, an application that issues the same query more than once might read additional rows, known as phantom rows, that were inserted and committed by a concurrently executing application process.

rebind
To create a new application plan for an application program that has been bound previously. If, for example, you have added an index for a table accessed by your application, you must rebind the application in order to take advantage of that index.

record
The storage representation of a row or other data.

record identifier (RID)
A unique identifier used internally by DB2 to identify a row of data in a table stored as a record. Compare with row ID.

record identifier (RID) pool
An area of main storage above the 16MB line that is reserved for sorting record identifiers during list prefetch processing.

recovery
The process of rebuilding databases after a system failure.

recovery log
A collection of records that describes the events that occur during DB2 execution and their sequence. The information recorded is used for recovery in the event of a failure during DB2 execution.

recovery pending (RECP)
This condition prevents SQL access to a table space or index space that may need to be recovered.

recovery token
An identifier for an element used in recovery. For example, NID or URID.

RECP
Recovery pending.

redo
A state of a unit of recovery which indicates that changes made are to be reapplied to the DASD media to ensure data integrity.

referential constraint
The requirement that nonnull values of a designated foreign key are valid only if they equal values of the primary key of a designated table.

referential integrity
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 enforcing referential constraints on all LOAD, RECOVER, INSERT, UPDATE, and DELETE operations.

referential structure
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.

registry
See registry database.

registry database
A database of security information about principals, groups, organizations, accounts, and security policies, that is maintained by the DCE security component.

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)
A relational database manager that operates consistently across supported IBM systems.

relational database name (RDBNAM)
A unique identifier for an RDBMS within a network. In DB2, this must be the value in the LOCATION column of table SYSIBM.LOCATIONS in the CDB. DB2 publications refer to the name of another RDBMS as a LOCATION value or a location name.

relationship
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)
The offset of a data record or control interval from the beginning of the storage space allocated to the data set or file to which it belongs.

remigration
The process of returning to a current release of DB2 following a fallback to a previous release. This procedure constitutes another migration process.

remote
Refers to any object maintained by a remote DB2 subsystem; that is, by a DB2 subsystem other than the local one. A remote view, for instance, is a view maintained by a remote DB2 subsystem. Contrast with local.

remote attach request
A request by a remote location to attach to the local DB2subsystem. Specifically, the request sent is an SNA Function Management Header 5.

remote subsystem
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 may even operate on the same processor under the same MVS system.

reoptimization
The DB2 process of reconsidering the access path of an SQL statement at run time, using the values of host variables, parameter markers, or special registers.

REORG pending (REORP)
A condition that restricts SQL access and most utility access to an object that must be reorganized.

REORP
See REORG pending.

repeatable read (RR)
The isolation level that provides maximum protection from other executing application programs. When an application program executes with repeatable read protection, rows referenced by the program cannot be changed by other programs until the program reaches a commit point.

request commit
The vote submitted to the prepare phase if the participant has modified data and is prepared to commit or roll back.

requester
Also application requester (AR). The source of a request to a remote RDBMS, the system that requests the data.

request unit (RU)
The part of a basic information unit that follows a request header and contains the data.

resource
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
The part of plan allocation that deals specifically with the database resources.

resource control table (RCT)
A construct of the Customer Information Control System attachment facility, created by site-provided macro parameters, that defines authorization and access attributes for transactions or transaction groups.

resource definition online
A Customer Information Control System feature that allows you to define Customer Information Control System resources on line without assembling tables.

resource limit facility (RLF)
A portion of DB2 code that prevents dynamic manipulative SQL statements from exceeding specified time limits.

resource limit specification table
A site-defined table that specifies the limits to be enforced by the resource limit facility.

restart pending (RESTP)
A restrictive state of a page set or partition which 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 by automatic online backout (invoked by DB2 after restart if system parameter LBACKOUT=AUTO).

RESTP
See restart pending.

result set
The set of rows returned to a client application by a stored procedure.

result set locator
A 4-byte value used by DB2 to uniquely identify a query result set returned by a stored procedure.

result table
The set of rows specified by a SELECT statement.

retained lock
A MODIFY lock that was held by a DB2 when that DB2 failed. The lock is retained in the coupling facility lock structure across a DB2 failure.

RID
See record identifier.

RID pool
Record identifier pool.

right outer join
The result of a join operation that includes the matched rows of both tables being joined and preserves the unmatched rows of the second join operand. See also join.

RLF
Resource limit facility.

RMID
Resource manager identifier.

RO
Read-only access.

rollback
The process of restoring data changed by SQL statements to the state at its last commit point. All locks are freed. Contrast with commit.

root page
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
Either auser-defined function or a stored procedure.

row
The horizontal component of a table. A row consists of a sequence of values, one for each column of the table.

ROWID
See row identifier.

row identifier (ROWID)
A value that uniquely identifies a row. This value is stored with the row and never changes.

row lock
A lock on a single row of data.

row trigger
A trigger defined with the trigger granularity FOR EACH ROW.

RRE
Residual recovery entry (IMS).

RTT
Resource translation table.

RRSAF
Recoverable Resource Manager Services attachment facility. A DB2 subcomponent that uses OS/390 Transaction Management and Recoverable Resource Manager Services to coordinate resource commitment between DB2 and all other resource managers that also use OS/390 RRS in an OS/390 system.

RU
Request unit.



S

SBCS
Single-byte character set.

SCA
See shared communications area.

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. See also column function.

scale
In SQL, the number of digits to the right of the decimal point (called the precision in the C language). The DB2 library uses the SQL definition.

schema
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. For example, the following statement creates a distinct type T in schema C: 
CREATE DISTINCT TYPE C.T ...

search condition
A criterion for selecting rows from a table. A search condition consists of one or more predicates.

secondary authorization ID
An authorization ID that has been associated with a primary authorization ID by an authorization exit routine.

secondary group buffer pool
For a duplexed group buffer pool, the structure 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.

section
The segment of a plan or package that contains the executable structures for a single SQL statement. For most SQL statements, there is one section in the plan for each SQL statement in the source program. However, for cursor-related statements, the DECLARE, OPEN, FETCH, and CLOSE reference the same section because they each refer to the SELECT statement named in the DECLARE CURSOR statement. SQL statements such as COMMIT, ROLLBACK, and some SET statements do not use a section.

segmented table space
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
A referential constraint that defines a relationship in which a table is a dependent of itself.

self-referencing table
A table with a self-referencing constraint.

sequential data set
A non-DB2 data set whose records are organized on the basis of their successive physical positions, such as on magnetic tape. Several of the DB2 database utilities require sequential data sets.

sequential prefetch
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
Also application server (AS). The target for a request from a remote RDBMS, the RDBMS that provides the data.

service class
An eight-character identifier that is used by MVS Workload Manager to associate customer performance goals with a particular DDF thread or stored procedure. Also used to classify work on parallelism assistants.

session
A link between two nodes in a VTAM network.

session protocols
The available set of SNA communication requests and responses.

shared communications area (SCA)
A coupling facility list structure used by a DB2 data sharing group for inter-DB2 communication.

shared lock
A lock that prevents concurrently executing application processes from changing data, but not from reading data.

shift-in character
A special control character (X'0F') used in EBCDIC systems to denote that the following bytes represent SBCS characters. See shift-out character.

shift-out character
A special control character (X'0E') used in EBCDIC systems to denote that the following bytes, up to the next shift-in control character, represent DBCS characters.

short string
A string whose actual length, or a varying-length string whose maximum length, is 254 bytes (127 double-byte characters) or less.

sign-on
A request made on behalf of an individual Customer Information Control System or IMS application process by an attach facility to enable DB2 to verify that it is authorized to use DB2 resources.

simple page set
A nonpartitioned page set. A simple page set initially consists of a single data set (page set piece). If and when that data set is extended to 2 gigabytes, another data set is created, and so on up to a total of 32 data sets. The data sets are considered by DB2 to be a single contiguous linear address space containing a maximum of 64 gigabytes. Data is stored in the next available location within this address space without regard to any partitioning scheme.

simple table space
A table space that is neither partitioned nor segmented.

single-byte character set (SBCS)
A set of characters in which each character is represented by a single byte.

single-precision floating point number
A 32-bit approximate representation of a real number.

SMF
System management facility.

SMP/E
System Modification Program/Extended.

SMS
Storage Management Subsystem.

SNA
Systems Network Architecture.

SNA network
The part of a network that conforms to the formats and protocols of Systems Network Architecture (SNA).

socket
A callable TCP/IP programming interface that is used by TCP/IP network applications to communicate with remote TCP/IP partners.

sourced function
A function that is implemented by another built-in or user-defined function 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 type
An existing type that is used to internally represent a distinct type.

space
A sequence of one or more blank characters.

special register
A storage area that is defined for a process by DB2 and is used to store information that can be referenced in SQL statements. Examples of special registers are USER, CURRENT DATE, and CURRENT TIME.

specific function name
A particular user-defined function 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 unique within its schema. Either the user or the default can provide this name.

SPUFI
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
Structured Query Language.

SQL authorization L ID)
The authorization ID that is used for checking dynamic SQL statements in some situations.

SQL Communication Area (SQLCA)
A structure used to provide an application program with information about the execution of its SQL statements.

SQL Descriptor Area (SQLDA)
A structure that describes input variables, output variables, or the columns of a result table.

SQL escape character
The symbol used to enclose an SQL delimited identifier. This symbol is the quotation mark ("). See escape character.

SQL ID
SQL authorization ID.

SQL path
(1) An ordered list of schema names 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 data, either through an application or by dynamic query requests.

SQL return code
Either SQLCODE or SQLSTATE.

SQL routine
A user-defined function or stored procedure based on code written in SQL.

SQL string delimiter
A symbol used to enclose an SQL string constant. The SQL string delimiter is the apostrophe ('), except in COBOL applications, in which case the symbol (either an apostrophe or a quotation mark) may be assigned by the user.

SQLCA
SQL communication area.

SQLDA
SQL descriptor area.

SQL/DS
SQL/Data System. Also known as DB2 for VSE & VM.

SSI
MVS subsystem interface.

SSM
Subsystem member.

stand-alone
An attribute of a program that means it is capable of executing separately from DB2, without using DB2 services.

statement string
For a dynamic SQL statement, the character string form of the statement.

statement trigger
A trigger defined with the trigger granularity FOR EACH STATEMENT.

static SQL
SQL statements, embedded within a program, that are prepared during the program preparation process (before the program is executed). After being prepared, the SQL statement does not change (although values of host variables specified by the statement might change).

storage group
A named set of DASD volumes on which DB2 data can be stored.

stored procedure
A user-written application program, that can be invoked through the use of the SQL CALL statement.

string
See character string or graphic string.

strong typing
Strong typing guarantees that only user-defined functions and operations 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, typically, provide a user-defined function to convert one currency to the other and then do the comparison.

structure
A construct used by MVS to map and manage storage on a coupling facility. See cache structure, list structure, or lock structure.

structure owner
In relation to group buffer pools, this is the DB2 member that is responsible for the following activities:

Structured Query Language (SQL)
A standardized language for defining and manipulating data in a relational database.

subcomponent
A group of closely related DB2 modules that work together to provide a general function.

subpage
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.

subselect
That form of a query that does not include ORDER BY clause, UPDATE clause, or UNION operators.

substitution character
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
A distinct instance of a RDBMS.

SVC dump
A dump that is issued when an MVS or a DB2 functional recovery routine detects an error.

sync point
See commit point.

syncpoint tree
The tree of recovery managers and resource managers involved in a logical unit of work, starting with the recovery manager, that makes the final commit decision.

synonym
In SQL, an alternative name 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 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. See also invariant character set.

Sysplex
A set of MVS systems that communicate and cooperate with each other through certain multisystem hardware components and software services to process customer workloads.

Sysplex query parallelism
Parallel execution of a single query accomplished by using multiple tasks on more than one DB2. See also query CP parallelism.

system administrator
The person having the second highest level of authority within DB2. System administrators make decisions about how DB2 is to be used and implement those decisions by choosing system parameters. They monitor the system and change its characteristics to meet changing requirements and new data processing goals.

system agent
A work request that DB2 creates internally such as prefetch processing, deferred writes, and service tasks.

system conversation
The conversation that two DB2s must establish to process system messages before any distributed processing can begin.

system diagnostic work area (SDWA)
The data that is recorded in a SYS1.LOGREC entry that describes a program or hardware error.

System Modification Program/Extended (SMP/E)
A tool for making software changes in programming systems (such as DB2 or MVS), and for controlling those changes.

Systems Network Architecture (SNA)
The description of the logical structure, formats, protocols, and operational sequences for transmitting information through and controlling the configuration and operation of networks.

SYS1.DUMPxx data set
A data set that contains a system dump.

SYS1.LOGREC
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 number of unordered rows. Synonymous with base table or temporary table.

table check constraint
A user-defined constraint that specifies the values that specific columns of a base table can contain.

table function
A function that receives a set of arguments and returns a table to the SQL statement that references the function. A table function can only be referenced in the FROM clause of a subselect.

table locator
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 space
A page set used to store the records in one or more tables.

table space set
A set of table spaces and partitions that should be recovered together because each of them contains a table that is a parent or descendent of a table in one of the others or because the set contains a base table and associated auxiliary tables. A table space set can contain both types of relationships.

task control block (TCB)
A control block used to communicate information about tasks within an address space that are connected to DB2. An address space can support many task connections (as many as one per task), but only one address space connection. See address space connection.

TCB
MVS task control block.

TCP/IP
A network communication protocol used by computer systems to exchange information across telecommunication links.

TCP/IP port
A 2-byte value that identifies an end user or a TCP/IP network application within a TCP/IP host.

temporary table
A table created by the SQL CREATE GLOBAL TEMPORARY TABLE statement that is used to hold temporary data. Contrast with result table and temporary table.

thread
The DB2 structure that describes an application's connection, traces its progress, processes resource functions, and delimits its accessibility to DB2 resources and services. Most DB2 functions execute under a thread structure. See also 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 a period.

ticket
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.

time
A three-part value that designates a time of day in hours, minutes, and seconds.

time duration
A decimal integer that represents a number of hours, minutes, and seconds.

timeout
Abnormal termination of either the DB2 subsystem or of an application because of the unavailability of resources. Installation specifications are set to determine both the amount of time DB2 will wait for IRLM services after starting, and the amount of time IRLM will wait if a resource requested by an application is unavailable. If either of these time specifications is exceeded, a timeout is declared.

time-sharing option (TSO)
Provides interactive time sharing from remote terminals.

timestamp
A seven-part value that consists of a date and time expressed in years, months, days, hours, minutes, seconds, and microseconds.

TMP
Terminal Monitor Program.

to-do
A state of a unit of recovery that indicates that the unit of recovery's changes to recoverable DB2 resources are indoubt and must either be applied to the DASD media or backed out, as determined by the commit coordinator.

trace
A DB2 facility that provides the ability to monitor and collect DB2 monitoring, auditing, performance, accounting, statistics, and serviceability (global) data.

transaction lock
A lock used to control concurrent execution of SQL statements.

transaction program name
In SNA LU 6.2 conversations, the name of the program at the remote logical unit that will be the other half of the conversation.

transition table
A temporary table that contains all the affected rows of the triggering table in their state before or after the triggering event occurs. Triggered SQL statements in the trigger definition can reference the table of changed rows in the old state or the new state.

transition variable
A variable that contains a column value of the affected row of the triggering table in its state before or after the triggering event occurs. Triggered SQL statements in the trigger definition can reference the set of old values or the set of new values.

trigger activation
The process that occurs when the trigger event 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
A set of SQL statements that are stored in a DB2 database and executed when a certain event occurs in a DB2 table.

trigger activation time
In a trigger definition, whether the trigger should be activated before or after the triggered event.

trigger body
The set of SQL statements that is executed when a trigger is activated and its triggered action condition evaluates to true.

trigger cascading
The process that occurs when the triggered action of a trigger causes the activation of another trigger.

triggered action
The SQL logic 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
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
The set of SQL statements that is executed when a trigger is activated and its triggered action condition evaluates to true. Also called trigger body.

trigger granularity
In the trigger definition, setting the number of times the triggered action is executed to once for the trigger event or once for each row that the trigger event affects.

trigger package
A package created when a CREATE TRIGGER statement is executed. The package is executed when the trigger is activated.

triggering event
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
The SQL operation that causes a trigger to be activated when performed on the triggering table.

triggering table
The table for which a trigger is created. When the defined triggering event occurs against this table, the trigger is activated.

TSO
Time-sharing option.

TSO attachment facility
A DB2 facility consisting of the DSN command processor and DB2I. Applications that are not written for the Customer Information Control System or IMSenvironments can run under the TSO attachment facility.

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 Version 4 or that are specified as type 1 indexes in Version 4. Contrast with type 2 indexes. As of Version 6, type 1 indexes are no longer supported.

type 2 indexes
Indexes that are created on a release of DB2 after Version 5 or that are specified as type 2 indexes in Version 4 or Version 5.



U

UDF
See user-defined function.

UDT
See user-defined data type.

uncommitted read (UR)
The isolation level that allows an application to read uncommitted data.

underlying view
The view upon which another view is directly or indirectly defined.

undo
A state of a unit of recovery that indicates that the changes made by the unit of recovery to recoverable DB2 resources must be backed out.

UNION
An SQL operation that combines the results of two select statements. UNION is often used to merge lists of values obtained from several tables.

unique index
An index which ensures that no identical key values are stored in a table.

uniqueness constraint
The rule that no two values in a primary key or key of a unique index can be the same.

unit of recovery
A recoverable sequence of operations within a single resource manager, such as an instance of DB2. 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 multi-site update operation, a single unit of work can include several units of recovery.

unlock
To release an object or system resource that was previously locked and return it to general availability within DB2.

untyped parameter marker
A parameter marker that is specified without its target data type. It has the form of a single question mark.

update trigger
A trigger defined with the triggering SQL operation UDPATE.

URE
Unit of recovery element.

URID (unit of recovery ID)
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-defined data type (UDT)
See distinct type.

user-defined function (UDF)
A function defined to DB2 using the CREATE FUNCTION statement that can be referenced thereafter in SQL statements. A user-defined function can be either an external function or a sourced function. Contrast with built-in function.

UT
Utility-only access.



V

value
The smallest unit of data manipulated in SQL.

variable
A data element that specifies a value that can be changed. A COBOL elementary data item is an example of a variable. Contrast with constant.

variant function
See not-deterministic function.

varying-length string
A character or graphic string whose length varies within set limits. Contrast with fixed-length string.

version
A member of a set of similar programs, DBRMs, packages, or LOBs.

view
An alternative representation of data from one or more tables. A view can include all or some of the columns contained in tables on which it is defined.

view check option
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 CREATE VIEW.

Virtual Telecommunications Access Method (VTAM)
An IBM licensed program that controls communication and the flow of data in an SNA network.

VSAM
Virtual storage access method.

VTAM
MVS Virtual telecommunication access method.