VMS Help SET, PREFERRED_PATH  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Access to a MSCP/TMSCP class device may be available to an
    OpenVMS node from more than one host or storage controller. Use
    the SET PREFERRED_PATH command to specify a particular host or
    preferred path to access a specific MSCP class disk or TMSCP
    class tape device.

    If a preferred path is specified, the normal OpenVMS path
    selection process is modified to select the user-specified path
    over other available paths, assuming the user-specified path is
    available.

    This command is only meaningful for MSCP/TMSCP class devices that
    have more than one path available.

    Format

      SET PREFERRED_PATH  device-name[:]

1 - Parameters

 device-name[:]

    Specifies the name of a MSCP class disk or TMSCP class tape
    device.

2 - Qualifiers

 2.1 - /HOST

       /HOST=host_name

    Tells the MSCP/TMSCP class driver that you want this host to
    be the preferred access path to the specified device. The class
    driver remembers this host name until it is changed by taking one
    of the following actions:

    o  Issuing another SET PREFERRED_PATH command specifying a
       different host

    o  Using the /NOHOST qualifier

    o  Rebooting the system

    Note that simply specifying a preferred path does not mean
    that it is immediately selected if the disk or tape device is
    currently using another path. Use the /FORCE qualifier along
    with the /HOST qualifier to force the preferred path to be used
    immediately.

    The host_name is the name of the host that will be the preferred
    path to the disk or tape device.

 2.2 - /FORCE

    Tells the class driver to initiate the path selection process
    immediately. If this qualifier is omitted when a new host name
    is specified, a switch from the current path to the new preferred
    path will not occur until some other event initiates the path
    selection process.

 2.3 - /NOHOST

    Clears any previously defined preferred path assignment. Restores
    usual OpenVMS path selection behavior.

3 - Examples

    1.$ SET PREFERRED_PATH $10$DUA10: /HOST=HSC014

      Prior to issuing this command, the $10$DUA10: disk device
      has host HSC015 as its primary path and host HSC014 as its
      secondary path. Issuing this command selects host HSC014 as the
      preferred path.

      Note that the preferred path has been recorded by the class
      driver; however, the disk will remain on the current path
      (HSC015) until the next time the path selection process is
      initiated.

    2.$ SET PREFERRED_PATH $10$DUA10: /HOST=HSC014 /FORCE

      To make the path change occur immediately, include the
      /FORCE qualifier on the command line with the preferred path
      specification.

    3.$ SET PREFERRED_PATH $10$DUA10: /FORCE

      Issue this command to initiate path selection processing if
      the specified device has a primary path that differs from the
      preferred path.

      If the preferred path is available, the device moves to that
      path.

    4.$ SET PREFERRED_PATH $10$DUA10: /NOHOST

      Remove the specified preferred path by using the /NOHOST
      qualifier if the device should no longer have a preferred path.