DBWR takes all CPU time

From: Ralf Hartmann <ralf_at_xsystem.de>
Date: Tue, 9 Mar 1999 21:53:03 +0100
Message-ID: <Pine.GSO.3.96.990309212549.2173A-100000@sunny>

We are running Oracle 8.0.5.1 on Sun Enterprise Server 3500 under Solaris 2.6 and noticed very poor performance writing db blocks to the disks.

Analyzing this problem we have figured out, that the DBWR process takes the full time of one cpu (66% user, 33 %sys) while the disks are not very busy (about 10-20 % shown by iostat).

We have done further tests with a "create table as select" statement on a raw device and on an ufs filesystem. The source table has 200 MBytes data.

On the ufs filesystem the server process of the "create table as select" uses 100 % of the CPU and the disk is about 30% busy. The statement tooks 4:30 minutes.

On the raw device the process uses less than 30% of one cpu and the disk is about 90% busy. The statement tooks 1:20 minutes.

Has anyone an idea, what is the problem with the filesystem?

We have figured out with truss, that kaoi() fails on the filesystem. But this should not cause such big differences in the performance.

Thanks
Ralf Hartmann

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Ralf Hartmann                           Tel.:   +49 89 746603 0
X-System GmbH                           Fax:    +49 89 746603 99
Bavariastr. 7a                          E-Mail: Ralf.Hartmann_at_Xsystem.De

80336 Muenchen Received on Tue Mar 09 1999 - 14:53:03 CST