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

    SWP_PRIO sets the priority of I/O transfers initiated by the
    swapper.

    This special parameter is used by Compaq and is subject to
    change. Do not change this parameter unless Compaq recommends
    that you do so.