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162 Administering dynamic multipathing (DMP)
Administering DMP using vxdmpadm
Displaying information about the DMP error-handling thread
To display information about the kernel thread that handles DMP errors, use the
following command:
# vxdmpadm stat errord
One daemon should be shown as running.
Configuring array policy modules
An array policy module (APM) is a dynamically loadable kernel module that may
be provided by some vendors for use in conjunction with an array. An APM
defines procedures to:
■ Select an I/O path when multiple paths to a disk within the array are
available.
■ Select the path failover mechanism.
■ Select the alternate path in the case of a path failure.
■ Put a path change into effect.
■ Respond to SCSI reservation or release requests.
DMP supplies default procedures for these functions when an array is
registered. An APM may modify some or all of the existing procedures that are
provided by DMP or by another version of the APM.
You can use the following command to display all the APMs that are configured
for a system:
# vxdmpadm listapm all
The output from this command includes the file name of each module, the
supported array type, the APM name, the APM version, and whether the module
is currently in use (loaded). To see detailed information for an individual
module, specify the module name as the argument to the command:
# vxdmpadm listapm module_name
To add and configure an APM, use the following command:
# vxdmpadm -a cfgapm module_name [attr1=value1 \
[attr2=value2 ...]]
The optional configuration attributes and their values are specific to the APM
for an array. Consult the documentation that is provided by the array vendor for
details.