Understanding the Cache Administration User Tablespace

TimesTen strongly recommends creating a separate tablespace for the cache administration user. This tablespace is used as the cache administration user's default tablespace. The tablespace contains autorefresh triggers for each Oracle database table, change log tables for each Oracle database table, and other objects that TimesTen needs for each cache administration user. If you do not specify a separate tablespace, then these objects are placed in the Oracle Database system tablespace.

Specify the tablespace when you create the cache administration user on the Oracle database. You can also specify the tablespace after user creation with the DEFAULT TABLESPACE clause of the Oracle Database ALTER USER statement.

Change log tables for each of the cached Oracle database tables reside in the cache administration user tablespace. For each update on an Oracle database table, one row (a change log record) is inserted into the change log table for that Oracle database table. The size of a change log record in bytes is as follows:

size of change log record = size of primary key on Oracle table + 250

The number of records in a change log table depends on the update rate on the Oracle database table and on the autorefresh interval on TimesTen. Every 20 seconds, TimesTen removes change log records that have been applied to all databases that cache the associated Oracle database table.

When change logs are removed, a message similar to the following is displayed in the support log:

16:32:26.73 Info: CAC: 5652: TT47112-5652-4756-ogTblGC01036: Garbage collector 
deleted 1 rows from TT_06_383270_L where logseq < 1

There are options on how to manage what happens when the cache administration user tablespace is filled. See Considerations When a Tablespace Is Full for more information.