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Changing the values of tunables

Tunables can be modified by editing the file /kernel/drv/vxio.conf for most VxVM tunables, or by editing the file /kernel/drv/vxdmp.conf for DMP tunables. The system must be shut down and rebooted for the change to take effect.

Warning: If you modify /kernel/drv/vxio.conf or /kernel/drv/vxdmp.conf, make a backup copy of the file.

For example, a single entry has been added to the end of the following /kernel/drv/vxio.conf file to change the value of vol_tunable to 5000:

name="vxio" parent="pseudo" instance=0


Warning: Do not edit the configuration file for the vxspec driver, /kernel/drv/vxspec.conf.

You can use the prtconf -vP command to display the current values of the tunables. All VxVM tunables that you specify in /kernel/drv/vxio.conf and /kernel/drv/vxdmp.conf are listed in the output under the "System properties." heading for the vxio and vxdmp drivers. All unchanged tunables are listed with their default values under the "Driver properties" heading. The following sample output shows the new value for vol_tunable in hexadecimal:

# prtconf -vP


vxio, instance #0

System properties:

name <vol_tunable> length <4>

value <0x00001388>

Driver properties:

name <voldrl_max_seq_dirty> length <4>

value <0x00000003>


For more information, see the prtconf(1M) and driver.conf(4) manual pages.

DMP tunables can also be set by using the vxdmpadm command as shown here:

# vxdmpadm settune dmp_tunable=value

The values of these tunables can be displayed by using this command:

# vxdmpadm gettune [dmp_tunable]

The vxdmpadm command also allows you to configure how DMP responds to I/O errors at the level of the paths to individual arrays.

See "Administering DMP using vxdmpadm" on page 150.