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RE: AIX and Largefiles Performance

From: Rich Holland <>
Date: Fri, 9 Jul 2004 16:18:59 -0400
Message-Id: <>


Any chance you can forward the tuning paper along? I'm interested in reading a copy. I'm currently running half a dozen ERP systems on Oracle 9204, AIX 51-003 and having no problems with the bf option on native JFS. From the tiny bit of reading I've done about JFS2, I'd worry more about performance there than via JFS -- I made the decision early on to stick with JFS, and haven't been disappointed. We've survived multiple power outage crashes, fibre channel disconnections, etc. It's been solid, and performed well -- we're using a pair of FCS adapters to SAN disk on an EMC via FC switches, and to be honest I don't think the client can generate enough workload to really stress the I/O configuration here... :-)


Rich Holland        (913) 645-1950        SAP Technical Consultant
print unpack("u","92G5S\=\"!A;F]T:&5R(\'!E<FP\@:&%C:V5R\"\@\`\`");

> -----Original Message-----
> From: [] On
> Behalf Of Byron Pearce
> Sent: Friday, June 25, 2004 3:51 PM
> To:
> Subject: AIX and Largefiles Performance
> All:
> I am not a native of Planet IBM, but this morning one of the systems
> administrators here forwarded over a tuning guide from the mother ship
> regarding Oracle on AIX. There were a number of interesting things in
> there that I am still working through, but one particular item piqued my
> interest.
> "... Do not allocate a JFS with the large file enabled (bf) attribute.
> The big file attribute increases the minimum DIO transfer size
> (diocapbuf.dio_min returned by the finfo system call) from 4K to 128K,
> forcing Oracle to read and write a minimum of 128K byte to exploit DIO.
> Please note that 2GB is the largest file size applications (including
> Oracle) can use in a JFS without the 'bf' attribute -- large file
> enablement. Do not allocate a compressed JFS, which defeats DIO.
> Respecting the JFS 2GB maximum file size avoids potential file level
> inode locking performance issues in JFS or JFS2 (without CIO), but a
> downside of small (2GB) files in a very large database (VLDB)
> environment is the time required to open/close files during the
> startup/shutdown."
> I have worked on most of the other major O/S variants, and this is the
> first time I have ever heard the largefiles settings have a negative
> impact on performance. In the interest of scientific investigation on
> this topic, I am officially checking my ego at the door and opening my
> mind to this possibility. I am trying to do some research on this, but,
> thus far, my findings have been sparse.
> Has anyone heard this before? Or is this a performance myth along the
> lines of the BCHR's (if so it is a first for me to hear it)? Or is
> there a genuine benefit to be gained by doing this?
> Any comments or thoughts on this matter would be appreciated.
> --
> ====================================================================
> Byron Pearce
> Tenure Systems, Inc. Dallas/Fort Worth, TX
> "It's hard to be a ninja when you wear a beeper."
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Received on Fri Jul 09 2004 - 15:17:16 CDT

Original text of this message