To improve performance of Replication Agent in an Oracle RAC environment, you can now:
Configure the Replication Agent for Oracle to use a multithreaded cluster log scanner for Oracle RAC replication. This decreases the amount of time between when a log record is written to the primary database log, and when it is first read by the Replication Agent. The lr_parallel_scan configuration property has been added to support this enhancement. lr_parallel_scan, is applicable to Oracle RAC only and determines whether the redo log threads for all nodes in a clustered database are scanned in parallel, or whether a single serial scan is used. The benefit of enabling parallel scan threads is improved performance and reduced read and process latency, because all redo log threads are scanned simultaneously. By default, this property is set to false. If set to true, additional system resources may be required and you may need to tune Replication Agent configuration properties.
Configure the Replication Agent for Oracle to generate commit log records in the primary database at a configured interval. If the primary database is a clustered database, the Replication Agent generates commit log records in each primary database node on the configured interval. This decreases process latency—the amount of time between when a log record is first read by the Replication Agent, and when it is then processed by the Replication Agent. These configuration properties and commands have been added to support this enhancement:
pdb_commit_generation – configuration property that determines whether committed transactions are generated in the primary database while the Replication Agent is in the replicating state. By default, this property is set to false.
pdb_commit_interval – configuration property that determines the interval, in seconds, at which committed transactions are executed in the primary database. The default value is 1 second.
pdb_commit_generation_status – a command that returns information and status for all primary database commit generation threads.
For the commit generation feature to work, pds_username must be
granted execute on dbms_lock privilege.
pdb_commit_generation_filter – a command that is used to modify the commit generation filter list. The filter list contains the list of Oracle instance names that should be filtered for commit generation. If an instance name is in the filter list, then commit generation does not occur against that instance when enabled.
To monitor the effectiveness of the commit generation feature, a new Log Reader (LR) statistic has also been added to the results of the ra_statistics command. The new statistic shows the average number of seconds between log record checkpoints. For Oracle RAC database replication, the statistic shows an average for each node in the cluster.
See the Replication Agent 15.5 Reference Manual.
