Database Tuning (MOSC)

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Low Cache Hit Ratio

edited Mar 15, 2010 6:38AM in Database Tuning (MOSC) 14 commentsAnswered
Hi All,

We use Automatic Shared Memory Management with the SGA_TARGET=2G. The database is 10.2.0.4 EE on RHEL5.
After the last restart of the database server, the db cache hit is around 70% and not increasing, where as it used to be between 95% to 99% earlier. How to tune buffer cache hit ratio in an automatic tuning scenario? Please suggest options apart from increasing SGA size. SGA is sized adequately and the problem showed up after a restart two days ago.

Currently The buffer cache is 960 MB.

Strangely the OEM shows around 90% cache hit ratio, where as while calculating through the formula it shows 73%. Below is the formula:

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