/sys$common/syshlp/helplib.hlb LINK, Qualifiers, /DSF  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /DSF[=file-spec]
       /NODSF (default)

    For Alpha linking, directs the linker to create a file called a
    debug symbol file (DSF) for use by the OpenVMS Debugger or the
    OpenVMS Alpha System-Code Debugger.

    The 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 use the .DSF file type.)