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

    (Alpha only) MPDEV_ENABLE enables the formation of multipath
    sets when set to ON (1).  If set to OFF (0), the formation
    of additional multipath sets is disabled. However, existing
    multipath sets remain in effect. The default is ON.