Oracle-L: RE: Free Buffer Waits

From: Cary Millsap <cary.millsap_at_hotsos.com>
Date: Thu, 13 Jun 2002 09:08:42 -0800
Message-ID: <F001.0047D508.20020613090842@fatcity.com>

"free buffer waits" waits indicate that your DBWR can't keep up with its workload. Often caused by inefficient SQL competing with DBWR for an I/O device.

Cary Millsap
Hotsos Enterprises, Ltd.
cary.millsap_at_hotsos.com
http://www.hotsos.com

-----Original Message-----
Zanen
Sent: Thursday, June 13, 2002 4:04 AM
To: Multiple recipients of list ORACLE-L

Hi All,

We have a production database that has a batch job running on it for months
now. Last night one part of the batch job that normally takes between 20-30
minutes took well over 6 hours.
The only difference I can see between today & other days is that the Free
Buffer Wait event was the top wait event, which it not normally is (not even top 10)

This database goes down every night for backup and this is the timings I got.

Total waits:22055
Total timeouts:22052
Time waited: 2225285 (is this ms or cs?) Avg.wait:100.8971

This whole thing puzzles me a bit since nothing changed to the database and
nothing was in the Alert log. Also system was virtually idle during the 6
hours (no activity according to UNIX boys)

I was sound asleep when this happened so I don't have much more than this
info.

Can anybody explain why this could have happened or point me to some documents that can. Standard answer you'll find that your DBWR can't keep
up, but I have 4 of them and the sytem was idle.

THX

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Author: Jack van Zanen
INET: nlzanen1_at_EY.NL

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Author: Cary Millsap
INET: cary.millsap_at_hotsos.com

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