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Parameter type
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Integer
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Default value
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All the buffers in the cache
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Parameter class
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Dynamic: ALTER SYSTEM
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Range of values
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1000 to all buffers in the cache. A setting of 0 disables limiting recovery I/Os.
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Real Application Clusters
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Multiple instances can have different values, and you can change the values at runtime.
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Note:
This parameter is deprecated in favor of the FAST_START_MTTR_TARGET parameter. Oracle recommends that you use FAST_START_MTTR_TARGET instead. FAST_START_IO_TARGETis retained for backward compatibility only.
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FAST_START_IO_TARGET (available only with the Oracle Enterprise Edition) specifies the number of I/Os that should be needed during crash or instance recovery.
When you set this parameter, DBWn writes dirty buffers out more aggressively, so that the number of blocks that must be processed during recovery stays below the value specified in the parameter. However, this parameter does not impose a hard limit on the number of recovery I/Os. Under transient workload situations, the number of I/Os needed during recovery may be greater than the value specified in this parameter. In such situations, DBWn will not slow down database activity.
Smaller values for this parameter result in faster recovery times. This improvement in recovery performance is achieved at the expense of additional writing activity during normal processing.
Setting this parameter to 0 disables fast-start checkpointing, which is the mechanism that limits the number of I/Os that need to be performed during recovery. All other writing activity is unaffected.
Notes:
Recovery I/O can also be limited by setting the LOG_CHECKPOINT_INTERVAL or LOG_CHECKPOINT_TIMEOUT parameter or by the size specified for the smallest redo log. For information on which mechanism is controlling checkpointing behavior, query the V$INSTANCE_RECOVERY view.
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