Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Configuring DMP path restoration policies
DMP maintains a kernel thread that re-examines the condition of paths at a
specified interval. The type of analysis that is performed on the paths depends
on the checking policy that is configured.
Note: The DMP path restoration thread does not change the disabled state of the
path through a controller that you have disabled using vxdmpadm disable.
When configuring DMP path restoration policies, you must stop the path
restoration thread, and then restart it with new attributes.
See “Stopping the DMP path restoration thread” on page 195.
Use the vxdmpadm start restore command to configure one of the following
restore policies. The policy will remain in effect until the restore thread is stopped
or the values are changed using vxdmpadm settune command.
■ check_all
The path restoration thread analyzes all paths in the system and revives the
paths that are back online, as well as disabling the paths that are inaccessible.
The command to configure this policy is:
# vxdmpadm start restore [interval=seconds] policy=check_all
■ check_alternate
The path restoration thread checks that at least one alternate path is healthy.
It generates a notification if this condition is not met. This policy avoids inquiry
commands on all healthy paths, and is less costly than check_all in cases
where a large number of paths are available. This policy is the same as
check_all if there are only two paths per DMP node. The command to configure
this policy is:
# vxdmpadm start restore [interval=seconds] \
policy=check_alternate
■ check_disabled
This is the default path restoration policy. The path restoration thread checks
the condition of paths that were previously disabled due to hardware failures,
and revives them if they are back online. The command to configure this policy
is:
# vxdmpadm start restore [interval=seconds] \
policy=check_disabled
Administering Dynamic Multi-Pathing
Administering DMP using vxdmpadm
194