RE: AIX 5.2 move from JFS to JFS2

  • From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>
  • To: <Patty.Charlebois@xxxxxxxxxxxxxx>, <Oracle-L@xxxxxxxxxxxxx>
  • Date: Wed, 27 Jun 2007 09:38:37 -0400


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
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: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Patty.Charlebois@xxxxxxxxxxxxxx
Sent: Wednesday, June 27, 2007 8:47 AM
To: Oracle-L@xxxxxxxxxxxxx
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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