Re: CPU_TIME > ELAPSED_TIME

Elapsed time and CPU time are not measured the same. Elapsed time is a stop watch. CPU time is a calendar with the rule that you get credit for the full day if you are present when the day starts.

You could be on the job for 10 minutes...but get credit for 24 hours if those 10 minutes started precisely at midnight. You could also be on the job for 23 hours and 50 minutes...and get no credit for hours because you were not on the job when the day started.

Cary Millsap covers this in his book "Optimizing Oracle Performance".

-- 
Daniel Fink

Oracle Performance, Diagnosis and Training

OptimalDBA    http://www.optimaldba.com
Oracle Blog   http://optimaldba.blogspot.com



Eagle Fan wrote:


> yes, I also thought about this possibility before.

>

> But this query is very simple, it's doing index unique scan on PK 

> index. buffer gets per execution is only 3.

>

> I can't image it run on multiple CPU at one time.

>

> What do you think?



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