Replication Agent statistics, analyzed over some amount of time, are used to identify bottlenecks in Replication Agent. The queue (or buffer) size statistics provide a likely indication of where a Replication Agent bottleneck is occurring. For example, if the Log Transfer Interface (LTI) inbound queue is at or near capacity, but the LTI outbound queue is at or near zero, the LTI inbound queue—where LTL is formatted—is probably the bottleneck decreasing replication performance. In this way, queue sizes can identify specific areas of trouble:
Queue bottleneck |
Cause |
|---|---|
An LTI outbound queue size at or near capacity |
Indicates that the Replication Agent is waiting on Replication Server. In this case, all queues in the Replication Agent will also be at or near capacity. |
An LTI inbound queue size at or near capacity but with an LTI outbound queue size at or near zero |
Indicates a bottleneck in Replication Agent LTL formatting. This may result from the primary database character set being different than the Replication Server character set, resulting in Replication Agent having to convert character data between character sets. Alternately, the bottleneck may result from the Replication Server RSSD not being used effectively, either because the RSSD is not being used at all—the use_rssd parameter is set to false—or because minimal columns functionality—as determined by the column_compression and lti_send_only_primary keys parameters—is not being used. |
A Log Reader operation queue size at or near capacity but with LTI queue sizes at or near zero |
Indicates a bottleneck in Replication Agent operation processing. This may result from a problem with RASD access or with a cache configuration. |
A queue size at or near zero |
May indicate a bottleneck on the log scan, since the Log Reader scan queue is the first queue used in Replication Agent processing. This bottleneck may result from input-output inefficiency, possibly due to the read block count being too low or to Replication Agent having to read a log over the network rather than locally. |
