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Re: distribution of the sleeps on the library cache latches

From: Edward Shevtsov <>
Date: Fri, 19 Oct 2001 03:26:18 -0700
Message-ID: <>

Hi Steve,

I had initiated the process of gradual migration to bind variables. It seems it will take a long time.
Thanks for your detailed answer, I appreciate it


> Hi Ed,
> Of course, I'd suggest that the application be enhanced to use bind
variables appropriately! ;-)
> In the interim, I would introduce a script such as 'keeper.sql' from the
Ixora web site to keep all the reusable
> material in the library cache so as to reduce the impact of the flushes.
Once that is working as desired, I would
> increase the flush frequency to an interval of say 1 hour or 30 minutes.
The size of the library cache and thus shared
> pool utilization will still grow over time, but more slowly. I would then
reduce the shared pool size to approximately
> the size that it grew to after 1 day of normal application usage. To then
mitigate the risk of ORA-4031 errors I would
> ensure that 'shared_pool_reserved_size' is allowed to default, but set
'_shared_pool_reserved_min_alloc' to its minimum
> value (which is 4000 or 5000, version dependent). An instance restart once
a week would be good too if you can manage
> that.
> @ Regards,
> @ Steve Adams
> @ - For DBAs
> @ - For Muslims
> @ - For all
> -----Original Message-----
> From: Edward Shevtsov []
> Sent: Friday, 19 October 2001 19:09
> To: Steve Adams;
> Subject: Re: distribution of the sleeps on the library cache latches
> Hi Steve,
> yes, you're absolutely right. I've inhereted that system. The
> shared_pool_size = 750M. I believe it's HUGE and oversized. The
> code is mostly based on literal SQL. The miss rate on the shared pool is
> normally about 15%-20% with periodical peaks up to 50%. But the previous
> insist that we shouldn't decrease the size of shared pool as the miss rate
> will be much higher. He also setup periodical flushing every 3 hours (I
> assume he did it in order to prevent ORA-4031).
> If I undestand the things right, deacresing of shared_pool_size will
> decrease load on shared pool latch _but_ contention on the library latches
> will be higher because of higher parse rate. Is it correct and what's your
> advice in my case?
> Thanks in advance,
> Ed

Please see the official ORACLE-L FAQ:
Author: Edward Shevtsov

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Received on Fri Oct 19 2001 - 05:26:18 CDT

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