Library /sys$common/syshlp/dbg$help.hlb DEBUG, SET, BREAK, Qualifiers, /EXCEPTION  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Causes the debugger to break whenever an exception is signaled.
    The break action occurs before any application-declared exception
    handlers are invoked.

    As a result of a SET BREAK/EXCEPTION command, whenever your
    program generates an exception, the debugger suspends program
    execution, reports the exception, and displays its prompt. When
    you resume execution from an exception breakpoint, the behavior
    is as follows:

    o  If you enter a GO command without an address-expression
       parameter, the exception is resignaled, thus allowing any
       application-declared exception handler to execute.

    o  If you enter a GO command with an address-expression
       parameter, program execution continues at the specified
       location, thus inhibiting the execution of any application-
       declared exception handler.

    o  On VAX, if you enter a STEP command, the debugger steps into
       any application-declared exception handler. If there is no
       application-declared handler for that exception, the debugger
       resignals the exception.

       On Alpha, you must explicitly set a breakpoint in the
       exception handler before entering a STEP or a GO command to
       get the debugger to suspend execution within the handler.

    o  If you enter a CALL command, the routine specified is
       executed.

    On Alpha processors, an exception might not be delivered (to
    the program or debugger) immediately after the execution of the
    instruction that caused the exception. Therefore, the debugger
    might suspend execution on an instruction beyond the one that
    actually caused the exception.