Improving the performance of single instance Oracle on file systems, January 2008

For ODM to function properly on HP-UX, the asynchronous disk device driver must be installed and

enabled for the Oracle instance.

When raw volumes are in use, you should disable ODM. The asynchronous disk device driver is

sufficient for providing the needed performance.

Enabling ODM

After installing the SG SMS bundles, the ODM library for Online JFS is in

/opt/VRTSodm/lib/libodm.sl.

After Oracle 9i or 10g is installed, a stub library is present in the $ORACLE_HOME/lib directory. The

following table shows the commands to enable and disable ODM for Oracle 9i and 10g.

Before performing these commands, you must shut down the Oracle database instance.

Table 1 Commands to enable and disable ODM

Oracle Database Action Commands

To enable ODM

ln –s /opt/VRTSodm/libodm.sl $ORACLE_HOME/lib/libodm9.so

Version 9i

To disable ODM

ln –s $ORACLE_HOME/lib/libodmd9.so libodm9.so

To enable ODM

ln –s /opt/VRTSodm/libodm.sl $ORACLE_HOME/lib/libodm10.so

Version 10g

To disable ODM

ln –s $ORACLE_HOME/lib/libodmd10.so libodm10.so

To verify that the ODM library is enabled, you can check the alert log after restarting the instance.

After starting the Oracle instance, the alert log will show:

Oracle instance running with ODM: VERITAS 4.1 ODM Library, Version 1.0

To verify that ODM is active, use the /opt/VRTS/bin/odmstat command, or examine the

/dev/odm/stats file, which contains aggregate statistics about the use of the ODM library by Oracle.

Online JFS File System Mount Options

When performing benchmark tests, it was important to consider the mount options used for the Oracle

data files and then to keep those mount options consistent across different measurements. The mount

options chosen were based on Oracle recommendations.

An experiment was performed with the Oracle database on raw VxVM v4.1, with and without ODM. With a workload of 140 clients, 43,984

TPMs were recorded (with ODM enabled) and 47,732 were recorded (with no ODM). Performance dropped when ODM was enabled on raw

VxVM volumes.

Refer to the Oracle Meta-link note 151719.1 (login required): “Performance Impact of file system when mounted as Buffered and Unbuffered

Option.”