/APPEND
       /NOAPPEND (default)

    If /APPEND is specified, the database is loaded with RMS $PUT
    operations. If the database already exists it will be appended
    to; if not, a new database will be created. Duplicate keys (left
    hand sides) will replace existing entries in databases created
    with /NODUPLICATE, so the last occurrence of a given key will be
    the one that is used.

    /NOAPPEND is a synonym for for /FAST_LOAD.