VMS Help DCE_IDL, DCL Command Interface, QUALIFIERS, /KEEP  *Conan The Librarian (sorry for the slow response - running on an old VAX)

      /KEEP [=option]
      /NOKEEP

        Specify one of the following options:

        ALL
        C_SOURCE
        NONE (equivalent to /NOKEEP)
        OBJECT (default)

        This qualifier is equivalent to the -keep file_types
        argument in the universal syntax.