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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Spotting the real cause of a Production slowdown (10g)
And to help find those same-but-for-literal-values SQLs (which typically have the same optimizer plan), you can use this query, which I have found very useful:
select plan_hash_value, count(*) from v$sql
where plan_hash_value > 0
group by plan_hash_value having count(*) > 4 --or whatever number you like
order by count(*);
Paul Baumgartel
paul.baumgartel_at_credit-suisse.com
212.538.1143
-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Dennis Williams
Sent: Thursday, April 20, 2006 9:44 AM
To: sac_at_uillinois.edu
Cc: oracle-l_at_freelists.org
Subject: Re: Spotting the real cause of a Production slowdown (10g)
Charles,
I have seen similar problems in earlier versions of Oracle - many literal statements and a large shared pool. Think about it -- when a new SQL statement is received, Oracle must check to see if it has ever received that statement before. The larger the shared pool, the more area it must scan. Of course, it doesn't find a match, so it must parse the new statement. Then it must find a spot in the shared pool to place the newly parsed statement. Which means it must age something out. And if the application is hammering Oracle with these statements inside a loop, it gets challenging for Oracle to keep up. If this is the situation, the answer is not to increase the size of the shared pool, because that just aggravates the problem.
Rather than looking for the single statement that is getting issued the most, you may want to look a lot of statements that are issued once but look very similar, like
select col1 from employee where empno = 1;
select col2 from employee where empno = 2;
In our case, the solution was to get the developers to recode the worst offenders to bind variables.
Also, you didn't mention which Oracle processes were consuming so much CPU.
Dennis Williams
http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html
-- http://www.freelists.org/webpage/oracle-lReceived on Thu Apr 20 2006 - 08:49:20 CDT
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