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Re: Important: Oracle processes taking lots of CPU

From: <>
Date: Tue, 23 Nov 2004 13:50:55 +0100
Message-ID: <>

I'm no expert here, but here *may be* a few things to think about: When Oracle is actually doing something it isn't recorded as a wait event, e.g. getting a datablock that is in cache doesn't generate a wait event. If your query is "horrible" you could be using loads of CPU without generating many waitevents.

A little more dodgy info: "db file sequential read" is normally accociated with datafile access by rowid, ie. after an index lookup.

I think I'd try to find out which queries are running during the performance problem times and explaining the queries.

Also, have you run spreport for this time period?

Told you I wasn't an expert, but I hope that prompts other readers to fill in the gaps and give you better hints,

Good luck

New DBA <> Sent by:
11/23/2004 11:57 AM
Please respond to


Important: Oracle processes taking lots of CPU

Hi all,
Please forgive my ignorance if the details provided by me are not sufficient, or I'm not doing proper analysis.
11.5.8 on O/s HP-UX Risc 64 B.11.11 We are facing a unique problem. Lots of DB processes take close to 100% CPU and an overall CPU time of more than 500 mins. This happens with lots of different applications/forms. The problem doesn't happen all the time i.e. if the same form is run 10 times, only 1-2 faces that kind of problem.
With my limited knowledge I've been able to get the following details about the problem.
The DB processes take a huge amount of CPU time. This fact is not reflected in v$sesstat or the 10046 trace files. There are processes which take more than 500 mins. of CPU time, but the trace file doesn't account for even a tiny fraction of that.
When monitoring the process at the OS, the process takes close to 100% CPU all the time, but the CPU stats in v$sesstat doesn't increase.
I did a truss on the processes consuming 100% CPU and it shows the following line repeating infinitely: select(2048, 0x800003fffdffb3d0, 0x800003fffdffb4d0, 0x800003fffdffb5d0, 0x800003fffdffb6d0) = 0 v$session_wait shows some wait event like "latch free", "db file sequential read" but with STATE = waited known time, but the seconds_in_wait keeps increasing while the process keeps taking 100% CPU all the while.
Please let me know if anyone has faced a similar issue. How do I find out what is the process doing which is eating up all the CPU?
I think that the problem is somehow at the O/S level, since trace files don't indicate anything wrong, same forms when run again, run without taking much CPU. Regards
New DBA                 

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-- Received on Tue Nov 23 2004 - 06:50:44 CST

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