RE: Cursor_sharing=similar.....failed

From: Kerber, Andrew W. <Andrew.Kerber_at_umb.com>
Date: Tue, 7 Aug 2007 10:51:43 -0500
Message-ID: <D40740337A3B524FA81DB598D2D7EBB3097A8829@x6009a.umb.corp.umb.com>

I cant tell you exactly what your issue is, but I know for a fact that cursor_sharing= similar or cursor_share=force both have serious issues in oltp systems. I suspect when a sql command wants to use the same cursor, it tries to use the same lock. Did Oracle advise you to implement cursor sharing? It can work wonders on a purely reporting system, but implementing it in a cerner environment strikes me as a poor idea.

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of daniel.hubler_at_aurora.org
Sent: Tuesday, August 07, 2007 10:06 AM
To: kurtvm_at_pandora.be
Cc: oracle-l_at_freelists.org
Subject: Re: Cursor_sharing=similar.....failed

Sorry......should have put that in...........

This is Oracle v9.2.0.5 running on OpenVMS v7.3-2

Dan Hubler
Database Administrator
Aurora Healthcare
Cerner Support Team
414-647-3257
daniel.hubler_at_aurora.org

"Kurt Van Meerbeeck" <kurtvm_at_pandora.be>

08/07/2007 10:00 AM

Please respond to
kurtvm_at_pandora.be

daniel.hubler_at_aurora.org, oracle-l_at_freelists.org

Subject

Re: Cursor_sharing=similar.....failed

What Oracle version - is this by any chance a 10.2.0.1 ?

cheers,
Kurt
----- Oorspronkelijk bericht -----
Van: daniel.hubler_at_aurora.org [mailto:daniel.hubler_at_aurora.org] Verzonden: dinsdag, augustus 7, 2007 04:12 PM Aan: oracle-l_at_freelists.org
Onderwerp: Cursor_sharing=similar.....failed

Looking for ideas/comments/suggestions..........

We changed cursor_sharing from EXACT to SIMILAR last Saturday morning at 6am.
Did that via an "ALTER SESSION SET....." command. The environment is large (7TB) but not very busy on Saturday morning. We had cursor_sharing=similar in multiple test environments, for many months without issue.

At 9:15am, we started to generated ora-04031 errors. By 9:30am, we could no longer sign-on.
We ended up shutting down the middle-tier, and deleting all of the OS processes on the DB server, that represented connections to the instance.
At that point, we were able to signon, backout the change, and startup the middle-tier again.

In the alert log, we saw the ora-04031 errors, and also many (thousands) of messages saying
"PMON failed to acquire latch, see PMON dump".

The PMON trace file show the same entry, repeated thousands of times:
"PMON unable to acquire latch 2c4cb108 library cache
possible holder pid = 1000 ospid=42586708"

Any ideas on what happened would be appreciated. Thanks.

Dan Hubler
Database Administrator
Aurora Healthcare
daniel.hubler_at_aurora.org

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Received on Tue Aug 07 2007 - 10:51:43 CDT