VMS Help SORT, Output File Qualifiers, /OVERLAY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies an existing empty file that the output file is to be
    overlaid, or written to. The /OVERLAY qualifier is required when
    you use the /INDEXED_SEQUENTIAL qualifier.

    Format

      output-file-spec/OVERLAY

  Additional Information (explode) :

• Full Description
• Example