Re: high db hit ratio and a lot of waits on db sequential reads
- From: genegurevich@xxxxxxxxxxxx
- To: fmhabash <fmhabash@xxxxxxxxx>
- Date: Fri, 28 Sep 2007 14:49:10 -0500
Hi, Fred,
I am trying to find out whether there is anything that I can do to reduce
the number of the waits. The average time
per wait varies befween 8 and 11ms according to Oracle's AWR. I see 1.6mil
LIO per sec and about 11 thousand
PIO per sec
thank you
Gene Gurevich
fmhabash
<fmhabash@xxxxxxx
om> To
Mark.Bobak@xxxxxxxxxxxxxxx
09/26/2007 11:12 cc
AM genegurevich@xxxxxxxxxxxx, oracle-l
<oracle-l@xxxxxxxxxxxxx>
Subject
Re: high db hit ratio and a lot of
waits on db sequential reads
For my edification, can you please provide these metrics ...
- LIO/sec
- PIO/sec
- if you look at your sql ordered by PIO, what do you see there. Can you
tell from the code what tables are being read from disk and why?
Also, on a finely tuned DB and in the absence of any other significant
wait events (e.g. log sync, scattered ...., etc), why wouldn't you
expect to see DBFSR as the top one. After all ,that's what the DB should
be doing serving user requests. The question, then, becomes how costly
it is. If you are doing less than 20ms, then you have no reason to loose
sleep over it (not that you are).
Thank you
Fred Habash, Lead Oracle DBA (OCP 8i,9i)
Oracle Team Portal http://spc-00sv0d03e3.spc.supc.com/ddcports/oracle/
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ACS HealthCare Solutions Dearborn, MI | Off.: 248-226-8778 |
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