The full command-line option is /[NO]WARNINGS=(option-list).

    Controls the severity level of messages and diagnostics. Valid
    options are:

    Option          Function

    WARNINGS        Display/suppress warnings.
    INFORMATIONALS  Display/suppress informationals.
    ALL             Display/suppress warnings and informationals.
    NONE            Display/suppress nothing.

    The default options are /WARNINGS=(WARNINGS,INFORMATIONALS). If
    more than one option is specified, options must be enclosed in
    parentheses separated by a comma.