XLA Tuning

There are tips on how you can improve XLA performance.

• Increase Transaction Log Buffer Size When Using XLA

• Prefetch Multiple Update Records

• Acknowledge XLA Updates

Increase Transaction Log Buffer Size When Using XLA

Performance impact: Large

A larger transaction log buffer size is appropriate when using XLA.

When XLA is enabled, additional transaction log records are generated to store additional information for XLA. To ensure the transaction log buffer is properly sized, one can watch for changes in the SYS.MONITOR table entries LOG_FS_READS and LOG_BUFFER_WAITS. For optimal performance, both of these values should remain 0. Increasing the transaction log buffer size may be necessary to ensure the values remain 0. See LogBufMB in the Oracle TimesTen In-Memory Database Reference.

Prefetch Multiple Update Records

Performance impact: Medium

Prefetching multiple update records at a time is more efficient than obtaining each update record from XLA individually. Because updates are not prefetched when you use AUTO_ACKNOWLEDGE mode, it can be slower than the other modes.

If possible, you should design your application to tolerate duplicate updates so you can use DUPS_OK_ACKNOWLEDGE, or explicitly acknowledge updates. Explicitly acknowledging updates usually yields the best performance if the application can tolerate not acknowledging each message individually.

Acknowledge XLA Updates

Performance impact: Medium

To explicitly acknowledge an XLA update, you call acknowledge on the update message. Acknowledging a message implicitly acknowledges all previous messages.

Typically, you receive and process multiple update messages between acknowledgements. If you are using the CLIENT_ACKNOWLEDGE mode and intend to reuse a durable subscription in the future, you should call acknowledge to reset the bookmark to the last-read position before exiting.