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Redo logfile switching / FAST_START_MTTR_TARGET / Automatic Checkpoint Tuning

edited Dec 12, 2011 9:58AM in Database Tuning (MOSC) 14 commentsAnswered ✓
DbAs...

My 11.2.0.1 Db was log switching every 9 minutes 'on average', so I followed past experience and increased the size of the 3 redo log group members by 70% to increase the time between checkpoints to roughly 15-20 minutes and thus reducing unneccessary DBWR/LGWR IO.

The surprise result was that now the logs are switching every 8 minutes (!) and inspection shows that the archive logs are only a fifth of the size of the online log - leading me to the obvious conclusion that checkpointing is not being caused by a full log.

Importanly, I have default values for all the standard documented parameters that influence checkpointing; including FAST_START_MTTR_TARGET (unset not disabled), LOG_CHECKPOINT_INTERVAL, and LOG_CHECKPOINT_TIMEOUT.

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