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Home -> Community -> Mailing Lists -> Oracle-L -> RE: free buffer waits & DISK I/O
Pablo,
Free buffer waits is normally due to DBWR not being able to write out modified blocks to disk fast enough.
By changing the disk layout you have eliminated disk contention and hot spots and have enabled DBWR to write out the dirty buffers to disk faster thus making enough free buffers available.
Steve Adams has an excellent paper on his website
"The Mysteries of DBWR Tuning".
http://www.ixora.com.au/tips/mystery.doc
Some of Steve's recommendation are to use asynchronous I/O, Spread datafiles across multiple disks, controllers and I/O busses to eliminate hot spots (that is what you probably did) and the use of raw datafiles.
Please see his paper for more in-depth detail.
Regards
Suhen
HI list.
I was tuning a database (Oracle 7.3.4) that was
waiting for "free buffer waits" mostly.
I tuned DBWn batch size properly (increased it till
4MB) as well as buffer cache size (it's 600MB now)
too and I got some improvement but I didn't get a
major improvement.
But some weeks ago, when we changed the disk array
(from one symmetrix to another) and made an appropiate
disk distribution (to eliminate contention), "free buffer waits" went down (almost desappeared). We didn't change anything else.
I noticed that the "avg db file parallel write" changed from 150ms to 30ms.
Can someone explain me why "free buffer waits" dissapeared?
TIA
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: =?iso-8859-1?q?Pablo=20ksksksk?= INET: p_rodri99_at_yahoo.es Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-LReceived on Mon Dec 17 2001 - 17:34:51 CST
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