• You must have permission to change file system behavior using the vxtunefs command to enable or disable Cached Quick I/O. By default, you need superuser (root) permissions to run the vxtunefs command, but other system users do not. Superuser (root) must specifically grant database administrators permission to use this command as follows:

  # chown root:db2iadm1 /opt/VRTS/bin/vxtunefs

  # chmod 4550 /opt/VRTS/bin/vxtunefs

  where users belonging to the db2iadm1 group are granted permission to run the vxtunefs command. We recommend this selective, more secure approach for granting access to powerful commands.

• You must enable Quick I/O on the file system. Quick I/O is enabled automatically at file system mount time.

If you have correctly enabled Quick I/O on your system, you can proceed to enable Cached Quick I/O as follows:

• Set the file system Cached Quick I/O flag, which enables Cached Quick I/O for all files in the file system.

• Setting the file system Cached Quick I/O flag enables caching for all files in the file system. You must disable Cached Quick I/O on individual Quick I/O files that do not benefit from caching to avoid consuming memory unnecessarily. This final task occurs at the end of the enabling process.

• If Cached Quick I/O is enabled, it is recommended that you monitor any paging activity to the swap device on your database servers. You can use the vmstat -I command to monitor swap device paging. If swap device paging is observed, proper AIX Virtual Memory Manager (VMM) tuning is required to improve database performance.