/sys$common/syshlp/helplib.hlb Sys Parameters, MPW_WAITLIMIT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    MPW_WAITLIMIT sets the number of pages on the modified-page list
    that causes a process to wait until the next time the modified-
    page writer writes the modified list. This parameter limits the
    rate at which any single process can produce modified pages. If
    this value is less than MPW_HILIMIT, a system deadlock occurs.
    The value for this parameter is normally equal to MPW_HILIMIT.

    MPW_WAITLIMIT has the AUTOGEN and DYNAMIC attributes.