the debugger will be unable to create a separate window; OSC not
 enabled.

    Facility: DEBUG, VMS Debugger

    Explanation: The debugger requires OSC support enabled to create
    a separate window (see SET MODE SEPARATE).

    User Action: To allow the debugger to create a separate window,
    type at DCL: DEFINE/SYSTEM UIS$VT_ENABLE_OSC_STRINGS TRUE. You
    may wish to put this line in your private startup file.