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Re: Max datafile size in AIX5.2L

From: Byron Pearce <>
Date: Tue, 29 Jun 2004 10:13:05 -0500
Message-ID: <>


I think you're referring to the post I put out on the list Friday. It was from an IBM document on Oracle Performance Tuning that said:

"... 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 never encountered this type of alleged issue on any other O/S (mainly Solaris and HPUX) so I was wondering if anyone had any experience or comments on it. I have not been able to wrangle resources to try and run some empirical tests at this point, but there is quite a bit of internal discussions (not heated just yet) starting to take place as a result of the doc.

Nuno Souto wrote:

> Wasn't there a warning a coupla days ago or so about
>AIX using 128Kb I/O block size (when using DIO?)
>for files >2Gb?

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 Tue Jun 29 2004 - 10:12:23 CDT

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