Oracle Metric Estimated MTTR

Oracle Consulting Tips by Burleson

The Estimated MTTR Oracle metric is the current estimated mean time to recover (MTTR) in the number of seconds based on the number of dirty buffers and log blocks (gives the current estimated MTTR even if FAST_START_MTTR_TARGET is not specified). MTTR is "mean time to recovery".

The MTTR was developed to measure the amount of downtime that will be incurred should there be a catastrophic failure of some component within the computer system. Of course, for continuously available systems the MTTR should be equal to zero, but many companies who are unable to invest many millions of dollars in continuous availability or often content to have systems with an MTTR which is measured in less than 30 minutes.

MTBF - Mean time Between Failures
- Hardware vendors can provide MTBF for all hardware.
- You must measure your companies MTBF, noting causes of outages (human, hardware, software)

MTTR - Mean Time To Recovery
- Sometimes MTTR depends of nature of failure
- Hardware vendors can guarantee MTTR, and this should be spelled-out in a binding contract.

Also see on MTTR:

Oracle Target MTTR

Oracle Estimated MTTR

Costs and Benefits for High Availability Oracle9i

Oracle 8i hidden database parameters

oracle 10g redo log sizing fast_start_mttr_target

Oracle documentation also offers information regarding the estimated MTTR metric. It explains that, The TARGET_MTTR field of V$INSTANCE_RECOVERY contains the MTTR target in effect. The ESTIMATED_MTTR field of V$INSTANCE_RECOVERY contains the estimated MTTR should a crash happen right away. Query these two fields to see if the system can keep up with your specified MTTR target." For the sample given, you may want to refer to this site.

This, and many other Oracle performance metrics are discussed in my book "Oracle Tuning" by Rampant TechPress. You can buy it directly from the publisher and save 30% at this link:

http://www.rampant-books.com/book_1002_oracle_tuning_definitive_reference_2nd_ed.htm

��