Multiple Scanners

Enable multiple scanner threads for RepAgent to take advantage of available replication paths and improve replication performance.

In multipath replication, there are multiple sender threads corresponding to the number of replication paths. However, RepAgent by default has only one scanner thread that can scan the primary database log and generate LTL commands sequentially for each sender thread, even if there are multiple replication paths from the primary database. Transactions with content that RepAgent needs to send through a dedicated path cannot be processed by the scanner till all the previous information in the log has been processed, and the single scanner thread needs to make a copy of the set of LTL commands for each path.

Multiple scanner threads dedicated to each path allow all the scanner threads to scan the database log and generate LTL commands in parallel, and:

Increase throughput by reducing the time that the sender thread waits for LTL commands from the scanner thread.
Reduce memory consumption because each scanner generates only the LTL commands that the respective path requires.

However, contention for resources increases with multiple scanners. Only enable multiple scanners if you decide that the default single scanner is adversely affecting multipath replication performance, and only if you have sufficient resources for multiple scanners.

Note: You must enable multiple scanners before you configure RepAgent to use the distribution by filter model of multipath replication.