RE: library cache hit ratio > 100% (science fiction answer content free reply)
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <jkstill@xxxxxxxxx>, <jhowerton@xxxxxxxxx>
- Date: Tue, 15 Mar 2005 11:05:17 -0500
Well, yesterday Oracle noticed that after you parsed, say, select * from
first_view_in_my_report_series, you next parsed select * from
second_view_in_my_report_series and Oracle looked at your system statistics
and memory usage and figured there was no real cost to parsing it whether
you wanted it later or not. Oracle didn't muddy your actual usage statistics
with its preemptive guesses, so you got a cache_hit on something you never
requested. Your database is really only tuned well if this number approaches
infinity, even if it means insisting that your users do exactly what they
did yesterday forevermore. If you have any questions about this, please
refer to my addition to the subject line.
Regards,
mwf
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Jared Still
Sent: Monday, March 14, 2005 4:13 PM
To: jhowerton@xxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: library cache hit ratio > 100%
My guess is that reloads has gone negative.
Which version of Oracle?
Jared
On Mon, 14 Mar 2005 14:47:05 -0600, James Howerton <jhowerton@xxxxxxxxx>
wrote:
> DBA's,
>
> Has anyone seen library cache hit ratio > 100% ??? This is a very busy
> production database, it is usually < 97 % ( I don't tune by hit ratios
> I'm just curious).
>
> SQL> select SUM(PINS)/(SUM(PINS)+SUM(RELOADS))*100
> from v$librarycache;
>
> Library Hit Ratio
> --------------------------
> 100.009799
>
> 1 row selected.
>
> TIA
> ...JIM...
> --
> //www.freelists.org/webpage/oracle-l
>
--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
--
//www.freelists.org/webpage/oracle-l
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//www.freelists.org/webpage/oracle-l
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