Re: Latch / Wait Events
Date: Thu, 12 Nov 2009 16:43:18 -0800 (PST)
Message-ID: <e15f532b-0f37-49d5-abf5-9e29bb8d3943_at_v25g2000yqk.googlegroups.com>
On Nov 12, 10:11 am, The Magnet <a..._at_unsu.com> wrote:
snip
> Hi,
>
> 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"
> , ADDR "sADDR"
> , GETS "sGETS"
> , MISSES "sMISSES"
> , SLEEPS "sSLEEPS"
> 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
Have you read Tom Kyte's books? That is where I would recommend you start at this point. Received on Thu Nov 12 2009 - 18:43:18 CST