VMS Help Sys Parameters, VBSS_ENABLE2  *Conan The Librarian (sorry for the slow response - running on an old VAX)

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

    This cell is used for enabling and disabling VBS dynamic
    capabilities that are valid only when VBS is enabled. The
    following table indicates the result for each value:

    Bit    Result

    0      Enables VBS to perform first-level data reduction when
           switching processes. The default is enabled.

    1      Enables VBS to perform second-level data reduction when
           switching processes. The default is enabled.

    2      Requests VBS to perform an optimization that detects empty
           private page table pages on the modified list and frees
           them directly to the free list versus writing them to the
           page file. The default setting is enabled.

    3-7    Reserved to Compaq for future use.