Limit Replication Transmitters, Receivers, and XLA Readers

Replication and XLA operations have significant overhead with transaction logging. Replication scales best when there are a limited number of transmitters or receivers.

Check your replication topology and see if you can simplify it. Generally, XLA scales best when there are a limited number of readers. If your application has numerous readers, see if you can reduce the number.

Monitor XLA and replication to ensure they are reading from the transaction log buffer rather than from the file system. With a lot of concurrent updates, replication may not keep up. Updates are single-threaded at the subscriber. You can achieve better XLA throughput if the frequency of acknowledgements is reduced.

Estimate the number of readers and transmitters required by checking the values in the LOG_FS_READS and LOG_BUFFER_WAITS columns in the SYS.MONITOR table. The system updates this information each time a connection is made or released and each time a transaction is committed or rolled back.

Setting LogFlushMethod=2 can improve performance of RETURN TWOSAFE replication operations and RETURN RECEIPT with DURABLE TRANSMIT operations.