VMS Help CMS, RESERVE, Qualifiers, /MERGE=generation-expression  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Controls whether another generation of the element (called the
    merge generation) is to be merged with the generation that is
    being reserved (called the retrieved generation).

    If you specify the /MERGE qualifier, CMS merges the lines of the
    two generations and delivers a single copy of the file to your
    default directory. The file that is placed in your directory has
    the current creation and revision times. The merge generation
    cannot be on the same line of descent as the retrieved generation.
    When there is a conflict between blocks of one or more lines, CMS
    includes the conflicting lines and flags the conflict.