RE: CIO & flash recovery area
- From: "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 18 Apr 2006 16:51:44 -0700
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@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Allen, Brandon
Sent: Monday, April 17, 2006 8:59 AM
To: oracle-l@xxxxxxxxxxxxx
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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