file-spec

    Specifies the character string you want the linker to use as the
    name of the debug symbol file. If you do not include a file type
    in the character string, the linker appends the .DSF file type to
    the file name.

    If you specify the /DSF qualifier without the file specification,
    the linker creates a debug symbol file with the file name of the
    first input file and the default file type .DSF. If you append
    the /DSF qualifier to one of the input file specifications, the
    linker creates a debug symbol file with the file name of the file
    to which the qualifier is appended and with the default file type
    .DSF.

    The OpenVMS Debugger (whether you use it in System-Code Debugger
    mode or user mode) requires that the name of the DSF file be
    the same as the name of the image file, except that the file
    extension is .DSF. If you use an /EXECUTABLE or /SHAREABLE
    qualifier and a file name with the LINK command, you must also
    include the same file name with the /DSF qualifier. (You must
    also use the .DSF file type.)