Re: High CPU usage by Oracle

From: <Jared.Still_at_radisys.com>
Date: Tue, 22 Jan 2002 10:56:55 -0800
Message-ID: <F001.003F781C.20020122102606@fatcity.com>

This query will show current sessions CPU usage. It may indicate a particular session is hogging the CPU.

select

   sess.username,
   stat.sid,
   name.name name,

sum(stat.value)/100 valuesum_seconds
from v$sesstat stat, v$statname name, v$session sess where

stat.sid = sess.sid
and stat.statistic# = name.statistic# and name.name like '%CPU%'
group by sess.username, stat.sid, name.name;

You should also use 'top' or some similar tool to identify the process.

At times a session may have a 'runaway' process that is hogging the CPU. If a single dedicated server process is using a very high percentage of the CPU, it's would probably be a good idea to kill it. Be sure to identify the user or batch program first to make sure it can be killed.

The output of 'ps -fuoracle' will show a dedicated session as similar to this:

oracleVDRPROD (DESCRIPTION=(LOCAL=no)(ADDRESS=(PROTOCOL=BEQ)))

The following query will match an
process to an Oracle session:

select

   s.username,
   s.sid,
   s.serial#,
   p.pid ppid,
   s.status,
   s.osuser,

substr(s.program,1,20) client_program, s.process client_process,
substr(p.program,1,20) server_program, p.spid server_pid
from v$session s, v$process p
where s.username is not null

use outer join to show sniped sessions in
v$session that don't have an OS process and p.addr(+) = s.paddr
uncomment to see only your own session --and userenv('SESSIONID') = s.audsid order by username, sid /

Jared

Uma Mohoni <umohoni_at_ikimbo.com>
Sent by: root_at_fatcity.com
01/22/02 07:20 AM
Please respond to ORACLE-L

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc: 
        Subject:        High CPU usage by Oracle

Hi,
I would like help with this problem I am grappling with since yesterday. One
of the test boxes with Sun Solaris 2.7 OS and Oracle 8.1.7.2 on it has started showing 97% and above CPU usage mostly by Oracle . It has slowed down the application to a point where the testers can not test. Does any one
have any idea why Oracle would suddenly hog CPU so much? The normal CPU usage on these boxes is 2%-3%. All help is greatly appreciated. Thanks in advance.

Thanks,
Uma Mohoni
Consultant, CDI Corporation
@ iKimbo Inc.
500-A Huntmar Park Drive
Herndon, VA 20170
(703) 904-4150 Ext:237
umohoni_at_ikimbo.com

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