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

    The SHADOW_SYS_TMO parameter has the following two distinct uses:

    o  At system boot time, when this is the first node in the
       cluster to boot and to create this specific shadow set. If the
       proposed shadow set is not currently mounted in the cluster,
       use this parameter to extend the time a booting system waits
       for all former members of the shadowed system disk to become
       available.

    o  Once the system successfully mounts the virtual unit and
       begins normal operations. In this usage, the SHADOW_SYS_
       TMO parameter controls the time the operating system waits
       for errant members of a system disk. (Use the SHADOW_MBR_TMO
       parameter to control the time the operating system waits for
       the errant members of an application disk.)

    This parameter applies only to members of the system disk shadow
    set. All nodes using a particular system disk shadow set should
    have their SHADOW_SYS_TMO parameter set to the same value once
    normal operations begin.

    The default value is 120 seconds. Change this parameter to a
    higher value if you want the system to wait more than the 120-
    second default for all members to join the shadow set. You can
    set the parameter value to 120 through 65,535 seconds.