Home » Oracle » 1z0-058 » Which two statements are true about Instance recovery in a RAC environment?
Which two statements are true about Instance recovery in a RAC environment?
A. Parallel instance recovery will work even If the RECOVERY_PARALLELISM initialization parameter is set to 0 or 1.
B. Increasing the size of the default buffer cache can speed up Instance recovery because instance recovery may use as much as 50 percent of the default buffer cache for recovery buffers.
C. The FAST_START_MTTR_TARGET initialization parameter includes both instance startup and recovery time.
D. The FAST_START_MTTR_TARGET initialization parameter specifies only the instance recovery time.
Correct Answer: BD
Explanation/Reference:
Instance Recovery and RAC
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.
In a single-instance environment, the instance startup combined with the crash recovery time is controlled by the setting of the FAST_START_MTTR_TARGET initialization parameter. You can set its value if you want incremental checkpointing to be more aggressive than the autotuned checkpointing. However, this is at the expense of a much higher I/O overhead.
In a RAC environment, including the startup time of the instance in this calculation is useless because one of the surviving instances is doing the recovery.
RECOVERY_PARALLELISM
RECOVERY_PARALLELISM specifies the number of processes to participate in instance or crash recovery. To force serial crash and instance recovery, set the RECOVERY_PARALLELISM parameter to 0 or 1. 0 or 1 disable parallel instance and crash recovery on a system that has multiple CPUs. An alert log displays the degree of parallelism that was chosen when the database instance/recovery starts.
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