Creating table spaces
Creating a table space within a database assigns containers to the table space and records its definitions and attributes in the database system catalog.
About this task
For automatic storage table spaces, the database manager assigns containers to the table space based on the storage paths associated with the database.
For non-automatic storage table spaces, you must know the path, device or file names for the containers that you will use when creating your table spaces. In addition, for each device or file container you create for DMS table spaces, you must know the how much storage space you can allocate to each container.
If you are specifying the PREFETCHSIZE, use a value that is a multiple of the EXTENTSIZE value. For example if the EXTENTSIZE is 10, the PREFETCHSIZE should be 20 or 30. You should let the database manager automatically determine the prefetch size by specifying AUTOMATIC as a value.
Use the keywords NO FILE SYSTEM CACHING and FILE SYSTEM CACHING as part of the CREATE TABLESPACE statement to specify whether the database manager uses Direct I/O (DIO) or Concurrent I/O (CIO) to access the table space. If you specify NO FILE SYSTEM CACHING, the database manager attempts to use CIO wherever possible. In cases where CIO is not supported (for example, if JFS is used), the database manager uses DIO instead.
When you issue the CREATE TABLESPACE statement, the dropped table recovery feature is turned on by default. This feature lets you recover dropped table data using table space-level restore and rollforward operations. This is useful because it is faster than database-level recovery, and your database can remain available to users. However, the dropped table recovery feature can have some performance impact on forward recovery when there are many drop table operations to recover or when the history file is very large.
If you plan to drop numerous tables and you use circular logging or you do not want to recover any of the dropped tables, disable the dropped table recovery feature by explicitly setting the DROPPED TABLE RECOVERY option to OFF when you issue the CREATE TABLESPACE statement. Alternatively, you can turn off the dropped table recovery feature after creating the table space by using the ALTER TABLESPACE statement.