ORACLE RAC指标 gc cr block flush time

gc cr block flush time

The CR block flush time is part of the service time for a CR buffer. The redo log write time and redo log sync time can influence the gc cr block flush time significantly.  Each individual start time is maintained in the request structure that is put on the log flush queue, the log flush duration is computed and the flush time statistics incremented when the request completes and is taken off the log flush queue.

 

A log flush for a cr block transfer is required when a cr buffer is cloned from a current buffer which has redo pending. A high percentage is indicative of hot blocks with frequent read after write access. Its probability can be computed by

 

  • V$CR_BLOCK_SERVER.FLUSHES / gc cr blocks served

 

and the average time in ms for a log flush would be

 

  • 10 * gc cr block flush time / V$CR_BLOCK_SERVER.FLUSHES

 

 

In Statspack, the average CR block flush time is displayed in the RAC Statistics section as

 

  • Avg global cache cr block flush time (ms)

 

Related statistics:

 

  • Redo write time

 

Related wait events

 

  • Log file sync
  • gc cr block busy

 

Refer to the statistic description for gc current block flush time for more information.

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