/sys$common/syshlp/helplib.hlb CMS, INSERT, GENERATION, Qualifiers, /SUPERSEDE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Controls whether CMS removes a generation of the element that
    exists in the class and replaces it with the specified generation.
    (Using /SUPERSEDE is the equivalent of using the REMOVE command
    before the INSERT command.)

    If you specify /SUPERSEDE and there is no generation of the
    specified element already in the class, an error message is
    issued and the generation is not inserted into the class. You
    cannot use the /IF_ABSENT qualifier on the same command line as
    the /SUPERSEDE qualifier to override this action.

    If you omit the /SUPERSEDE qualifier and a generation of the
    element already exists in the class, an error message is issued
    and no change is made to the library.