Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

Enabling Cached Quick I/O on a file system

Cached Quick I/O depends on Veritas Quick I/O running as an underlying system

enhancement in order to function correctly. Follow the procedures listed here to

ensure that you have the correct setup to use Cached Quick I/O successfully.

■ 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.

Prerequisites

Enabling and disabling the qio_cache_enable flag

As superuser (root), set the qio_cache_enable flag using the vxtunefs command

after you mount the file system.

Improving DB2 database performance with Veritas Cached Quick I/O

Enabling Cached Quick I/O on a file system