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RE: AIX 5.2 move from JFS to JFS2

From: Bobak, Mark <>
Date: Wed, 27 Jun 2007 09:38:37 -0400
Message-ID: <>


Of course, since you just moved from 9.2 to 10.2, you mean db_cache_size, not db_block_buffers, right? ;-) I don't have any firsthand experience w/ JFS2, however, yes, in general, it's certainly possible to see physical I/O increase, as Oracle now has to physically hit disk for data that was previously cached in the filesystem buffer cache. This is ok though, the idea is that Oracle is much smarter about caching stuff than the filesystem is, since it has more information. So, there should have been some memory freed up, when you moved to JFS2 and CIO. That memory should be allocated to the database buffer cache, to compensate. In the end, you should come out ahead. Finally, if you really want to get bang for your buck on caching, you may consider implementing a keep and a recycle pool. I have done this to great effect in the past.

Hope that helps,


Mark J. Bobak
Senior Oracle Database Administrator, System & Product Technologies ProQuest
789 E. Eisenhower, Parkway, P.O. Box 1346 Ann Arbor MI 48106-1346
734.997.4059 or 800.521.0600 x 4059

ProQuest...Start here.

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

From: [] On Behalf Of Sent: Wednesday, June 27, 2007 8:47 AM
Subject: AIX 5.2 move from JFS to JFS2

Now that I have upgraded our production systems from to I can see via truss that Oracle is taking advantage of our newly implemented JFS2 filesystems and opening the datafiles using CIO.

We are experiencing higher WIO percentages since the upgrade.

My sysadmn has suggested that perhaps I need to increase db_block_buffers to make up for the lack of buffering at the FS level now that we are using JFS2.

Does anyone have any experience and/or thoughts regarding this?


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-- Received on Wed Jun 27 2007 - 08:38:37 CDT

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