RE: CIO & flash recovery area

No replies yet to my initial inquiry, so I guess nobody is running their flash recovery areas on a cio filesystem. Oracle support referred me to the following link: http://www.rampant-books.com/t_oracle_direct_i_o.htm - which says "Oracle recommends that all database files use Direct I/O XE "Direct I/O" , which is a disk access method that bypasses the additional overhead on the OS buffer. One important exception to this rule is the archived redo log filesystem which should use OS buffer caching."  

Can anyone think of a reason why archived redo logs should be buffered instead of direct/concurrent I/O? It doesn't make sense to me.  

Thanks,
Brandon    

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Allen, Brandon Sent: Monday, April 17, 2006 8:59 AM
To: oracle-l_at_freelists.org
Subject: CIO & flash recovery area

Howdy list,  

Oracle support can't answer this question, so I'm turning to y'all. I'm setting up a new 10.2.0.2 database on AIX 5.3 and have set filesytemio_options=setall in order to enable CIO (concurrent I/O) on the datafiles, and I have mounted the filesystems for the redologs with cio and agblksize=512. All good there. My question is on how to configure the filesystem for the flash recovery area - should it also be mounted with cio and agblksize=512? I'm thinking cio would be good for this filesystem since the same blocks aren't likely to be accessed repeatedly, there is no point in keeping them in the filesystem buffer cache, right? Regarding the setting of agblksize, I think it depends on the I/O size Oracle uses to access the files in the flash recovery area (flashback database log, archived redo logs, datafile copies, etc.). I'm guessing that archive logs are written in 512 byte blocks just like the online redo, but I don't know if that's true or not. Do any of you know? Is anyone else running your flash recovery area on CIO - what have your experiences been?  

Thanks,
Brandon    

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http://www.freelists.org/webpage/oracle-l Received on Tue Apr 18 2006 - 18:51:44 CDT