screen mode is not supported on this device screen mode output is
 being lost

    Facility: DEBUG, VMS Debugger

    Explanation: The debugger output is being sent to a device that
    the Screen Management Facility does can not write to. While
    the debugger will continue to process commands, the screen mode
    output will be lost.

    User Action: Make sure the logical DBG$OUTPUT is pointed to a
    device that the Screen Management Facility can write to.