Re: CPU Time

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Sun, 9 Jan 2005 15:01:40 -0000
Message-ID: <023301c4f65c$1fca1ce0$6702a8c0@Primary>

The question is almost meaningless.

Note first that the report is heading "Top 5 TIMED events" not "Top 5 WAIT events".

Now consider this - if you have used 4 CPU seconds in 1 elapsed second, what percentage of your CPU have you used ? It depends on the number of CPUs

If you have waited for Disk I/O for 20 seconds in one elapsed second, how long (on average) has each user waited ? It depends on the number of concurrent users requesting disk I/O in that period.

It was (in some ways) a big mistake for Oracle to put the CPU usage exactly where they did; although it is a very important number to have available when you are looking at the wait events.

Ignore the CPU percentage from statspack. Factor in the number of CPUs, the number of concurrent active users, the elapsed time of the report. And even then you haven't shown any reason why you might need to change anything.

Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk/faq/ind_faq.html The Co-operative Oracle Users' FAQ

http://www.jlcomp.demon.co.uk/seminar.html Public Appearances - schedule updated Dec 23rd 2004

Original Message ----- From: "Jaffar_DBA" <sjaffarhussain_at_gmail.com> To: "Active DBA" <oracle-l_at_freelists.org> Sent: Sunday, January 09, 2005 1:48 PM Subject: CPU Time

Hello list,

If I have CPU time as my top most wait, what should I look for reducing it? Below are my top fives events and almost always, the top wait event is CPU Time .

Top 5 Timed Events

~~~~~~~~~~~~~~~~~~                                                     % 
Total
Event                                               Waits    Time (s) Ela

Time
-------------------------------------------- ------------ ----------- --------
CPU time

4,625 91.49

db file sequential read                            95,317         140 
2.76
log file sync                                            47,051
 118     2.33
log file parallel write                                55,772
79     1.56
SQL*Net more data to client                    46,977          69     1.36

Application background:

My application is an oline share trading application. We have only 3 hours in the morning and 3 hours in the evening trading session.

--

Best Regards,
Jaffar, OCP DBA
Banque Saudi Fransi
Saudi Arabia
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http://www.freelists.org/webpage/oracle-l

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http://www.freelists.org/webpage/oracle-l Received on Sun Jan 09 2005 - 08:57:01 CST