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abnormal use of CPU by oracle 9.0.1 with MTS

TOMAS BERNABEU
Frequent Advisor

abnormal use of CPU by oracle 9.0.1 with MTS

Hello!
I have oracle 9.0.1-4 in raw device mode and MTS. 3,5 GB SGA ( 1,2 GB shared area). The system cpu mode is very high ( 80 % ), and its consumption is in the system call mmap and nunmap. some idea to correct this?

Tom
8 REPLIES
Steve Steel
Honored Contributor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

HI

guess is that you are out of memory and it swaps a lot

post

swapinfo -tm

Check for dbc_max_pct in kernel


Steve Steel
If you want truly to understand something, try to change it. (Kurt Lewin)
TOMAS BERNABEU
Frequent Advisor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

Hi steve !

don´t have swap problems

dbc_mac_pct = 2 % because don'nt work with
file systems. works with raw volumes with async mode access and Virtual Array.

Sys Mem : 500.3mb
User Mem: 5.97gb
Phys Mem: 10.0gb
Active VM: 398.7mb
Buf Cache: 204.8mb
Free Mem: 3.34gb
users = 200 to 9
Brian Crabtree
Honored Contributor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

1. Is this causing a performance hit?

2. What is the process name that is taking up the CPU? (If it is 'oracleSID ...' then it is an Oracle client connection)

3. Have you considered upgrading to 9.2.0? 9.0.1 was the initial 9i version, and had a number of bugs against it. This could be a bug that has already been resolved.

Thanks,

Brian
Patrick Wallek
Honored Contributor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

dbc_max_pct has nothing to do with swap.

Do a 'swapinfo -tam' and see what you get.

My next thought is your 'timeslice' kernel parameter. If you happened to apply one of the "tuned parameter sets" then they set timeslice to 1, which it should never be. If it is set to 1, change it back to 10 as soon as you can.
Hein van den Heuvel
Honored Contributor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

1) I strongly agree witht the earlier comment about upgrading to Oracle 9.2(.0.4)
I don't think there can be an application constraint/incompatibility to stop you from doing that. But of cours you'll need to set aside the time to do it.

2) Are you sure you still have a need for MTS or is that perhpas a carry over from an old installation? The primary objective of using MTS tends to be to reduce memory usage. You seem to have enough of that ?!

3) The real question.. that high CPU usage... have you 'chattered' the Oracle image ? check 'chatr $ORACLE_HOME/bin/oracle'. You probably want pi=16M and pd=L

hth,
Hein.
TOMAS BERNABEU
Frequent Advisor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

hello!
I changed mts because my sga is great ( 1,2 GB Shared area), and a high number of connections needed to reserve to much swap,
(around 29 GB for 500 conections/users ).
The change to mts has reduced radically to this problem, reducing drastically the use of memory and disc.
But the CPU use way system has increased enormously. To change to the 9,2 to change, is not very scientist.
It interests to me to resist your opinions.
Thanks
Tom
Hein van den Heuvel
Honored Contributor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

Hmmm 29GB for 500 users is a tad high.
60MB / user of private space?
Using a lot of 'retained sort area' ?
PGA target way high?
That memory usage may well be warranted but is not typical and begs for a solid explanation... or mabye a fix!
Checked those pagesize attributes with chatr?

Hein.
Brian Crabtree
Honored Contributor

Re: abnormal use of CPU by oracle 9.0.1 with MTS

Thomas,

Hein brought up a good point. Have you considered setting pga_aggregate_target instead of using the specific parameters. This could help with the memory impact from the connections. Again, 9.2.0 has a number of new features (V$PGA_TARGET_ADVICE) which can help tune this parameter (which can be changed dynamiclly).

Also, I'm not sure what you meant to say about not upgrading to 9.2.0. Oracle 9.0 was the first release set for 9i, which means that a number of changes have been made between them. It should also be noted that 9.0 has been desupported from ECS.

http://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_database_id=NOT&p_id=201685.1

Thanks,

Brian