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Changing the values of tunables

To display the current value of a tunable that is being used by VxVM or DMP, use the following commands with the /proc file system:

# cat < /proc/sys/vxvm/vxio/vol_maxio


# cat < /proc/sys/vxdmp/dmp_enable_restore_daemon


To change the value of a VxVM or DMP tunable, specify the new value using the vxvoltune and vxdmptune commands:

# vxvoltune vxvm_tunable value

# vxdmptune dmp_tunable value

You must then shut down and reboot the system for the change to take effect. The new value persists across system reboots until it is next changed.

For example, the following command sets the value of vol_maxio to 8192:

# vxvoltune vol_maxio 8192

Warning: The vxvoltune and vxdmptune utilities modify the tunable values stored in the /etc/vx/vxvm_tunables and /etc/vx/vxdmp_tunables files respectively. It is recommended that you use the vxvoltune and vxdmptune commands to change the values stored in these files. Do not edit these files directly.

You can use the vxvoltune and vxdmptune commands to display the current values of a tunable parameter that is set in the vxvm_tunables and vxdmp_tunables files:

# vxvoltune vxvm_tunable

# vxdmptune dmp_tunable

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

# vxdmpadm settune dmp_tunable=value

A value that is set in this way overrides that defined in the /etc/vx/vxdmp_tunables file.

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.