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

       /DIAGNOSTICS[=filespec]
       /NODIAGNOSTICS (default)

    Creates a file containing assembler messages and diagnostic
    information. If you omit the file specification, the default file
    name is the same as the source program; the default file type is
    DIA.

    No wildcard characters are allowed in the file specification.

    The diagnostics file is reserved for use with Compaq layered
    products, such as the VAX Language-Sensitive Editor (LSE).