Eliminating Disk I/O Bottlenecks

I/O activity can cause bottlenecks for both Extract and Replicat.

• A regular Extract generates disk writes to a trail and disk reads from a data source.

• Each process writes a recovery checkpoint to its checkpoint file on a regular schedule.

Improving I/O performance Within the System Configuration

If there are I/O waits on the disk subsystems that contain the trail files, put the trails on the fastest disk controller possible.

Check the RAID configuration. Because Oracle GoldenGate writes data sequentially, RAID 0+1 (striping and mirroring) is a better choice than RAID 5, which uses checksums that slow down I/O and are not necessary for these types of files.

Improving I/O Performance Within the Oracle GoldenGate Configuration

You can improve I/O performance by making configurations changes within Oracle GoldenGate. Try increasing the values of the following parameters.

• Use the CHECKPOINTSECS parameter to control how often Extract and Replicat make their routine checkpoints.

  Note: CHECKPOINTSECS is not valid for an integrated Replicat on an Oracle database system.

• Use the GROUPTRANSOPS parameter to control the number of SQL operations that are contained in a Replicat transaction when operating in its normal mode. Increasing the number of operations in a Replicat transaction improves the performance of Oracle GoldenGate by reducing the number of transactions executed by Replicat, and by reducing I/O activity to the checkpoint file and the checkpoint table, if used. Replicat issues a checkpoint whenever it applies a transaction to the target, in addition to its scheduled checkpoints.

  Note: GROUPTRANSOPS is not valid for an integrated Replicat on an Oracle database system, unless the inbound server parameter parallelism is set to 1.

• Use the EOFDELAY or EOFDELAYCSECS parameter to control how often Extract or Replicat checks for new data after it has reached the end of the current data in its data source. You can reduce the system I/O overhead of these reads by increasing the value of this parameter. Note: Increasing the values of these parameters improves performance, but it also increases the amount of data that must be reprocessed if the process fails. This has an effect on overall latency between source and target. Some testing will help you determine the optimal balance between recovery and performance.