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Re: Library cache latch contention

From: Ricky Sanchez <rsanchez_at_more.net>
Date: Sun, 02 Mar 2003 04:39:19 GMT
Message-ID: <3E618AE7.8A7EFAC3@more.net>


Dias-

You really are not providing enough information here to offer serious analysis. You don't tell us how latch free waits relate to other wait events. Nor do you compare library cache latch sleeps to other latches. The raw numbers by themselves really don't say much.

And, how does the first sampling period compare to the second?

Why not zip up and post before and after statspacks? Makes a meaningful opinion possible.

dias wrote:
>
> Hi,
>
> I observed the following stats on a 9.0.1 (os is tru64) database about
> "libary cache latch". The application is an industrial one with only
> small stored PL/SQL procedures.
>
> The first report:
>
> LATCH_NAME GETS MISSES HIT_RATIO SLEEPS
> SLEEPS/MISS
> ------------------ ----------- ----------- ----------- -----------
> -----------
> library cache 1021637 126 1 108618601
> 862052.389
>
> After setting session_cached_cursors = 100, and cursor_sharing = FORCE
> (the application does not use bind variables):
>
> LATCH_NAME GETS MISSES HIT_RATIO SLEEPS
> SLEEPS/MISS
> ------------------ ----------- ----------- ----------- -----------
> -----------
> library cache 988150 34 1 31887719
> 937874.088
>
> There is no reloads. The v$sgastat reports 50 Mo of free memory, the
> shared pool is about 100 Mo. The time waited for latch free is very
> small (the average wait is 0).
>
> The question is, what causes a lot of sleeps over this latch ?
>
> Thanks
Received on Sat Mar 01 2003 - 22:39:19 CST

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