Re: CPU Time

  • From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
  • To: "Active DBA" <oracle-l@xxxxxxxxxxxxx>
  • Date: Sun, 9 Jan 2005 15:01:40 -0000

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.


Jonathan Lewis
The Co-operative Oracle Users' FAQ
Public Appearances - schedule updated Dec 23rd 2004

----- Original Message ----- 
From: "Jaffar_DBA" <sjaffarhussain@xxxxxxxxx>
To: "Active DBA" <oracle-l@xxxxxxxxxxxxx>
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
~~~~~~~~~~~~~~~~~~                                                     % 
Event                                               Waits    Time (s) Ela 
-------------------------------------------- ------------ ----------- --------
CPU time
   4,625    91.49
db file sequential read                            95,317         140 
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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