Using Classic Capture in an Oracle RAC Environment

The following general guidelines apply to Oracle RAC when Extract is operating in classic capture mode.

During operations, if the primary database instance against which Oracle GoldenGate is running stops or fails for any reason, Extract abends. To resume processing, you can restart the instance or mount the Oracle GoldenGate binaries to another node where the database is running and then restart the Oracle GoldenGate processes. Stop the Manager process on the original node before starting Oracle GoldenGate processes from another node.
Whenever the number of redo threads changes, the Extract group must be dropped and re-created. For the recommended procedure, see Administering Oracle GoldenGate.
Extract ensures that transactions are written to the trail file in commit order, regardless of the RAC instance where the transaction originated. When Extract is capturing in archived-log-only mode, where one or more RAC instances may be idle, you may need to perform archive log switching on the idle nodes to ensure that operations from the active instances are recorded in the trail file in a timely manner. You can instruct the Oracle RDBMS to do this log archiving automatically at a preset interval by setting the archive_lag_target parameter. For example, to ensure that logs are archived every fifteen minutes, regardless of activity, you can issue the following command in all instances of the RAC system:
```
SQL> alter system set archive_lag_target 900
```
To process the last transaction in a RAC cluster before shutting down Extract, insert a dummy record into a source table that Oracle GoldenGate is replicating, and then switch log files on all nodes. This updates the Extract checkpoint and confirms that all available archive logs can be read. It also confirms that all transactions in those archive logs are captured and written to the trail in the correct order.

The following table shows some Oracle GoldenGate parameters that are of specific benefit in Oracle RAC.

Parameter Description

Parameter	Description
`THREADOPTIONS` parameter with the `INQUEUESIZE` and `OUTQUEUESIZE` options	Sets the amount of data that Extract queues in memory before sending it to the target system. Tuning these parameters might increase Extract performance on Oracle RAC.
`TRANLOGOPTIONS` parameter with the `PURGEORPHANEDTRANSACTIONS \| NOPURGEORPHANEDTRANSACTIONS` and `TRANSCLEANUPFREQUENCY` options	Controls how Extract handles orphaned transactions, which can occur when a node fails during a transaction and Extract cannot capture the rollback. Although the database performs the rollback on the failover node, the transaction would otherwise remain in the Extract transaction list indefinitely and prevent further checkpointing for the Extract thread that was processing the transaction. By default, Oracle GoldenGate purges these transactions from its list after they are confirmed as orphaned. This functionality can also be controlled on demand with the `SEND EXTRACT` command in GGSCI.

THREADOPTIONS parameter with the INQUEUESIZE and OUTQUEUESIZE options

Sets the amount of data that Extract queues in memory before sending it to the target system. Tuning these parameters might increase Extract performance on Oracle RAC.

TRANLOGOPTIONS parameter with the PURGEORPHANEDTRANSACTIONS | NOPURGEORPHANEDTRANSACTIONS and TRANSCLEANUPFREQUENCY options

Controls how Extract handles orphaned transactions, which can occur when a node fails during a transaction and Extract cannot capture the rollback. Although the database performs the rollback on the failover node, the transaction would otherwise remain in the Extract transaction list indefinitely and prevent further checkpointing for the Extract thread that was processing the transaction. By default, Oracle GoldenGate purges these transactions from its list after they are confirmed as orphaned. This functionality can also be controlled on demand with the SEND EXTRACT command in GGSCI.

Parent topic: Additional Configuration Steps for Using Classic Capture