Latch / Wait Events

From: The Magnet <>
Date: Thu, 12 Nov 2009 07:11:50 -0800 (PST)
Message-ID: <>


I've been reading some documentation on latches to try and see if our database can be improved. While the concept is rather simple, I cannot really find information on which latches are really important and what numbers may indicate a problem.

We have many, many events "rdbms ipc message". Some values are:

Total Waits: 27674285
Timeouts: 535295
Time Waited: 164032311

If this bad? Why are the so many of these events?

Here is another one related to redo logs:

log file parallel write
Total Waits: 27705118
Total Timeouts: 0
Time Waited: 983231

This query has been posted everywhere. I've run it for 3 days and the same addresses appear at the top:

select CHILD# "cCHILD"


     from v$latch_children
     where name = 'cache buffers chains'
     order by 5 desc, 1, 2, 3;

sMisses: 364252
sSleeps: 8957

This good or bad???

I know that any value for 'cache buffers chains' or 'latch_free' is probably not good. But, how to decide what latch wait is bad, what value is unacceptable and what can be done?

We are running 10gR2.

Many Thanks Received on Thu Nov 12 2009 - 09:11:50 CST

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