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

 condition

    Specifies either the severity level of an error or a Ctrl/Y
    interrupt. Specify one of the following keywords, which may be
    abbreviated to one or more characters:

    WARNING        Return status of warning occurs ($SEVERITY equals
                   0).

    ERROR          Return status of error occurs ($SEVERITY
                   equals 2).

    SEVERE_ERROR   Return status of error occurs ($SEVERITY
                   equals 4).

    CONTROL_Y      Ctrl/Y character occurs on SYS$INPUT.

    The default error condition is ON ERROR THEN EXIT.

 command

    Specifies the DCL command line to be executed. Optionally, you
    can precede the command line with a dollar sign ($).

    If you specified an error condition as the condition parameter,
    the action is taken when errors equal to or greater than the
    specified level of error occur.