Re: select for update wait issues

From: Mladen Gogala <mgogala_at_yahoo.com>
Date: Mon, 13 Apr 2015 12:53:07 -0400
Message-ID: <552BF473.5090901_at_yahoo.com>

On 04/13/2015 12:25 PM, Sandra Becker wrote:
> Oracle 11.2.0.2
> Solaris 10 64-bit on Oracle T5
> EMC storage (fast cache enabled)
>
> Last Wednesday night we moved a production database to new hardware.
> We do not have the option to move it back. On Friday we started
> experiencing severe performance issues. ASH reports show the
> "SELECT...FOR UPDATE WAIT..." running as the top SQL for events and
> row sources. This is NOT new code. What can I look at, is there
> anything I can do, short of killilng sessions, to get this under
> control? I'm opening a ticket with Oracle, but this forum generally
> responds faster.
>
> I'm not really familiar with how the SELECT FOR UPDATE WAIT works and
> haven't found a good explanation yet. The select is on a partitioned
> table. Does it lock only a row or does it lock the partition? At
> times I can see a dozen or more of these statements running. Once
> they complete, I then see a lot of waits on log file sync.
>
> If anyone knows, how does having fast-cache enabled affect this?
>
> Thanks for any suggestions/guidance.
>
> --
> Sandy
> GHX
Hi Sandra,
What event exactly are your sessions waiting on? Regards,

-- 
Mladen Gogala
Oracle DBA
http://mgogala.freehostia.com

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Received on Mon Apr 13 2015 - 18:53:07 CEST