Oracle Database Discussions

Hi Guys,

I understand that high db cache hit ratio doesn't indicates that the database is healthy.
The database might be doing additional "physical" reads due to un-tuned SQL.

However, can explain why a low cache hit ratio might not indicate the db is unhealthy, as in the db need additional memory allocated?
What i can think of is probably:

1. the database might query different data most of the time. As such the data is not read again from cache before it aged out. Even if i add additional memory, the data might not be read again (from memory).
2. ?
3. ?

I'm quite reluctant to list out the databases with below 90% hit ratio as part of the monthly report to the management. To them, below 90% means unhealthy.
If these ratios to be used in monthly report, there will be a long section to explain why these ratios cannot meet but there is no performance concern.

As such will need your expert advise on this.

thanks

Edited by: Chewy on Mar 13, 2012 1:23 AM