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

    MPW_LOLIMIT sets a lower limit for the modified-page list. When
    writing of the list causes the number of pages on the list to
    drop to or below this limit, writing stops.

    MPW_LOLIMIT ensures that a certain number of pages are available
    on the modified-page list for page faults. If the number is
    too small, the caching effectiveness of the modified-page list
    is reduced. If it is too high, less memory is available for
    processes, so that swap (and page) may increase.

    MPW_LOLIMIT has the AUTOGEN and GEN attributes.