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Message-ID: <4899E390.8030503@gmail.com>
Date: Wed, 06 Aug 2008 12:46:56 -0500
From: Riyaj Shamsudeen <riyaj.shamsudeen@gmail.com>
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To: kmoore@zephyrus.com
CC: oracle-l <oracle-l@freelists.org>
Subject: Re: 10046 trace - unaccounted for time
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Reply-to: riyaj.shamsudeen@gmail.com

Hi Keith
  That means that process is either running on CPU or waiting for CPU in 
the run queue, to be available. May be that all buffers it is trying to 
access is in buffer cache and process is running on the CPU without any 
waits.

Cheers
Riyaj
The Pythian Group
blog: http://orainternals.wordpress.com

Keith Moore wrote:
> Oracle 9.2.0.4, Solaris
>
> We are having a production issue where user processes are very slow. We are
> seeing 'cache buffers chains' latch events in the 10046 trace file.
>
> What I'm not fully understanding is the long periods of unaccounted for time
> where the process hangs. If I do a 'tail -f' on the trace file I can see it
> pause for several seconds. Here is a small sample of the output:
>
> *** 2008-08-05 15:22:57.748
> WAIT #23: nam='latch free' ela= 8 p1=16764558008 p2=98 p3=0
> WAIT #23: nam='latch free' ela= 12 p1=16764645560 p2=98 p3=0
> *** 2008-08-05 15:23:16.414
> WAIT #23: nam='latch free' ela= 9 p1=16796730344 p2=98 p3=0
> WAIT #23: nam='latch free' ela= 10 p1=16764600056 p2=98 p3=0
> WAIT #23: nam='db file sequential read' ela= 1893 p1=66 p2=52489 p3=1
> *** 2008-08-05 15:23:33.376
> WAIT #23: nam='latch free' ela= 8 p1=16764602936 p2=98 p3=0
> *** 2008-08-05 15:23:47.319
> WAIT #23: nam='latch free' ela= 7 p1=16796666408 p2=98 p3=0
>
> If you look at the first four lines, you see 20 seconds have elapsed but the
> only wait events are the two 'cache buffers chains' waits for a total of 20
> microseconds.
>
> Can someone explain what is going on here and how to troubleshoot?
>
> FYI, this process is deleting and the inserting a LOB and the hot blocks seem
> to be in the LOB index.
>
> Thanks
> Keith
>
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>
>   

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