/DIAGNOSTICS[=file-spec]
  /NODIAGNOSTICS            (D)

  Creates a diagnostic file containing compiler messages and
  diagnostic information.  The diagnostic file is reserved for use by
  HP.  The Language-Sensitive Editor (LSE) uses the diagnostic file
  to display diagnostic messages and to position the cursor on the line
  and column where a source error exists.  The default file type for a
  diagnostic file is DIA.

  The default, /NODIAGNOSTICS, suppresses the creation of a diagnostic
  file.