SQL Reference

Table Spaces and Other Storage Structures

Storage structures contain the objects of the database. The basic storage structures managed by the database manager are table spaces. A table space is a storage structure containing tables, indexes, large objects, and data defined with a LONG data type. There are two types of table spaces:

Database Managed Space (DMS) Table Space

A table space which has its space managed by the database manager.

System Managed Space (SMS) Table Space

A table space which has its space managed by the operating system.

All table spaces consist of containers. A container describes where objects, such as some tables, are stored. For example, a subdirectory in a file system could be a container.

For more information on table spaces and containers, see CREATE TABLESPACE or the Administration Guide.

Data that is read from table space containers is placed in an area of memory called a buffer pool.

A buffer pool is associated with a table space allowing control over which data shares the same memory areas for data buffering. For more information on buffer pools, see CREATE BUFFERPOOL or the Administration Guide.

A partitioned database allows data to be spread across different database partitions. The partitions included are determined by the nodegroup assigned to the table space.

A nodegroup is a group of one or more partitions that are defined as part of the database. A table space includes one or more containers for each partition in the nodegroup. A partitioning map is associated with each nodegroup. The partitioning map is used by the database manager to determine which partition from the nodegroup will store a given row of data. For more information on nodegroups and data partitioning, see Data Partitioning Across Multiple Partitions, CREATE NODEGROUP or the Administration Guide.

A table can also include columns that register links to data stored in external files. The mechanism for this is the DATALINK data type. A DATALINK value which is recorded in a regular table points to a file stored in an external file server.

The DB2 Data Links Manager, which is installed on a fileserver, works in conjunction with DB2 to provide the following optional functionality:

• Referential integrity to insure that files currently linked to DB2 are not deleted or renamed.
• Security to insure that only those with suitable SQL privileges on the DATALINK column can read the files linked to that column.
• Coordinated backup and recovery of the file.

The DB2 Data Links Manager product comprises the following facilities:

Data Links File Manager

Registers all the files in a particular file server that are linked to DB2.

Data Links Filesystem Filter

Filters file system commands to insure that registered files are not deleted or renamed. Optionally also filters commands to insure that proper access authority exists.

For more information on DB2 Data Links Manager refer to Administration Guide.