VMS Help SET, COMMAND, Qualifiers, /REPLACE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies /REPLACE mode to add or replace verbs in the command
    table you are modifying.

    You can use the /REPLACE qualifier to modify either the process
    command table or a command table file specified with the /TABLE
    qualifier. If you do not use the /TABLE qualifier to specify an
    alternate command table, the default is to modify your process
    command table. If you do not use the /OUTPUT qualifier to specify
    an output file, the default is to return the modified command
    table to your process.

    You cannot use the /OBJECT or /DELETE qualifiers in /REPLACE
    mode.

    If you do not explicitly specify /DELETE, /OBJECT, or /REPLACE
    mode, the default is /REPLACE.