Re: Max datafile size in AIX5.2L

Nuno:

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                         mailto:pearceb@xxxxxxxxxx
Tenure Systems, Inc.                 Dallas/Fort Worth, TX

"It's hard to be a ninja when you wear a beeper."



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