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

    NOCLUSTER controls whether page read clustering is inhibited
    when the system boots. Set NOCLUSTER to 1 (inhibit page read
    clustering) only for debugging purposes.

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