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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.

Use the start restore command to configure one of the following policies:

• 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 policy=check_all [interval=seconds]

• 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 policy=check_alternate \

  [interval=seconds]

• 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 policy=check_disabled \

  [interval=seconds]

• check_periodic

  The path restoration thread performs check_all once in a given number of cycles, and check_disabled in the remainder of the cycles. This policy may lead to periodic slowing down (due to check_all) if there is a large number of paths available. The command to configure this policy is:

# vxdmpadm start restore policy=check_periodic \

  interval=seconds [period=number]

The interval attribute must be specified for this policy. The default number of cycles between running the check_all policy is 10.

The interval attribute specifies how often the path restoration thread examines the paths. For example, after stopping the path restoration thread, the polling interval can be set to 400 seconds using the following command:

# vxdmpadm start restore interval=400

To change the interval or policy, first stop the path restoration thread, and then restart it with new attributes.

See "Stopping the DMP path restoration thread" on page 157.