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

    The debugger consists of two parts: A main debugger image
    (DEBUGSHR.EXE) that contains most of the debugger code and
    a smaller kernel debugger image (DEBUG.EXE). This separation
    reduces potential interference between the debugger and the
    program being debugged and also makes it possible to have a
    multiprocess debugging configuration.

    When you start the debugger, a process is created to run the
    main debugger. Regardless of the configuration (default or
    multiprocess), the presence of a main debugger running in some
    process establishes a unique debugging session.

    When you bring a program under debugger control, the main
    debugger spawns a subprocess to run the program along with the
    kernel debugger.

    In the multiprocess configuration, the program being debugged
    runs in several processes. Each process that is running one or
    more images under debugger control is also running a local copy
    of the kernel debugger. The main debugger, running in its own
    process, communicates with the other processes through their
    kernel debuggers.

    Although all processes of a multiprocess configuration must be in
    the same job, they do not have to be related in a particular
    process/subprocess hierarchy. Moreover, the program images
    running in separate processes do not have to communicate with
    each other.