RE: filesystemio_options setting

From: Herring Dave - dherri <>
Date: Wed, 14 May 2008 06:50:32 -0500
Message-ID: <>

We ran into a related problem on RHEL 4 and After changing from ASYNCH to SETALL, after some amount of time CTAS statements were dragging along at 50 MB/s. After changing back to ASYNCH the same statements ran at 400 MB/s. Changing back again to SETALL caused those same statements, after running for x amount of time, to gradually drop again to 50 MB/s.

I've never had time to fully investigate this, so I can't say for sure that SETALL was the culprit but it sure seemed that way after a few, basic tests. This behavior is opposite of what I would have expected, as it seemed that the addition of DIRECTIO seemed to slowly fill up something, killing throughput. Yet DIRECTIO should be bypassing filesystem cache so it shouldn't be affected by any memory-related setting. Trying to explain this now has me REALLY curious as to what was happening. Great, more work!


Dave Herring, DBA |   A c x i o m  M I C S / C S O 630-944-4762 office | 630-430-5988 wireless | 630-944-4989 fax

From: [] On Behalf Of John Smith Sent: Tuesday, May 13, 2008 10:19 PM
Subject: filesystemio_options setting

Hi.  We are running oracle on our test evironment in suse 9.   Emc symmetrix storage.  I was going over the settings and discovered that filesystemio_options was not set (no value given).  I changed it to setall per the Oracle documentation for Linux.  Shortly after that, our queries suddenly started running longer, and the culprit appears to be disk IO. 

I understood that this setting could not cause a problem, and all the Oracle documentation I could find said to set this value to setall in  I unset the value and the problem went away. Can someone shed some light on this?

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Received on Wed May 14 2008 - 06:50:32 CDT

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