Thursday, April 5, 2012

Instance Recovery and RAC

Here are some guidelines you can use to make sure that instance recovery in your RAC environment is faster:

Use parallel instance recovery by setting RECOVERY_PARALLISM.
Increase PARALLEL_EXECUTION_MESSAGE_SIZE from its default of 2,148 bytes to 4 KB or 8 KB. This should provide better recovery slave performance.
Set PARALLEL_MIN_SERVERS to CPU_COUNT-1. This will prespawn recovery slaves at startup time.
Using asynchronous I/O is one of the most crucial factors in recovery time. The first-pass log read uses asynchronous I/O.
Instance recovery uses 50 percent of the default buffer cache for recovery buffers. If this is not enough, some of the steps of instance recovery will be done in several passes. You should be able to identify such situations by looking at your alert.log file. In that case, you should increase the size of your default buffer cache.

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