Configuring a Transaction Log File Threshold for AWT Cache Groups

In TimesTen Classic, the replication agent uses the transaction log to determine which updates on cache tables in AWT cache groups have been propagated to the cached Oracle Database tables and which updates have not. If updates are not being automatically propagated to the Oracle database because of a failure, transaction log files accumulate on the file system.

Examples of a failure that prevents propagation are that the replication agent is not running or the Oracle database server is unavailable. See Monitoring Accumulation of Transaction Log Files in Oracle TimesTen In-Memory Database Operations Guide.

You can call the ttCacheAWTThresholdSet built-in procedure as the TimesTen cache administration user to set a threshold for the number of transaction log files that can accumulate before TimesTen Classic stops tracking updates on cache tables in AWT cache groups. The default threshold is 0. This built-in procedure can only be called if the TimesTen database contains AWT cache groups.

After the threshold has been exceeded, you need to manually synchronize the cache tables with the cached Oracle Database tables using an UNLOAD CACHE GROUP statement followed by a LOAD CACHE GROUP statement. TimesTen may purge transaction log files even if they contain updates that have not been propagated to the cached Oracle Database tables.

The following example sets a transaction log file threshold for AWT cache groups. In this example, if the number of transaction log files that contain updates on cache tables in AWT cache groups exceeds 5, TimesTen stops tracking updates and can then purge transaction log files that may contain unpropagated updates:

% ttIsql "DSN=cache1;UID=cacheadmin;PwdWallet=/wallets/cacheadminwallet"
Command> CALL ttCacheAWTThresholdSet(5);

You can call the ttCacheAWTThresholdGet built-in procedure to determine the current transaction log file threshold setting:

Command> CALL ttCacheAWTThresholdGet;
< 5 >
Command> exit