Tales From A Lazy Fat DBA

One of the crucial performance parameter for Golden gate extract process is TRANLOGOPTIONS which controls the way that it interacts with the transaction log. You can use multiple TRANLOGOPTIONS statements in the same parameter file, or you can specify multiple options within the same TRANLOGOPTIONS statement.

There are lot of performance related options i.e. INCLUDEAUX (AUX trails when reading audit trails), DBLOGREADERBUFSIZE etc. that you can use with TRANLOGOPTIONS parameter, but recently I’d tried one of the tuning parameter PERFORMANCEPROFILE with our medium intensity workload. It can be set to HIGH and MEDIUM (default). It helps achieve better performance by grouping the parameters that affect performance. Once the performance profile is set up, this option automatically configures the applicable parameters, to achieve the desired throughput and latency.

We’d used this parameter in one of our 21c (21.7.0) GG installation with TRANLOGOPTIONS PERFORMANCEPROFILE HIGH, but immediately we’d started seeing spikes in extract’s latency. This was might be because it increases the Extract’s read buffer size to 8MB and the rule to purge the extract read buffer is either when the buffer is full or there is no ingress records for 0.2 seconds. Therefore, any uninterrupted workload with Extract consumption rate below 8MB will result in integrated Extract latency to exceed 1 second.

We’d checked with Oracle support and as a quick temporary solution they’d suggested to not use PERFORMANCEPROFILE parameter with HIGH flag, as the Extract consumption/intake rates are below specific value, such as ~15 MB/sec to get ~0.5 second extract response times. Hence we’d set the buffer size to one-third of the redo generation rate in MB/sec to get ~0.3 second maximum Extract latency. They also marked this as Bug 33772499 for GG 21c for July 2022 release.

Hope It Helped!
Prashant Dixit