/WAIT (default)
       /NOWAIT

    Controls whether the debugging session (the parent process) is
    suspended while the subprocess is running. The /WAIT qualifier
    (default) suspends the debugging session until the subprocess
    is terminated. You cannot enter debugger commands until control
    returns to the parent process.

    The /NOWAIT qualifier executes the subprocess in parallel with
    the debugging session. You can enter debugger commands while the
    subprocess is running. If you use /NOWAIT, you should specify
    a DCL command with the SPAWN command; the DCL command is then
    executed in the subprocess. A message indicates when the spawned
    subprocess completes.

    The kept debugger (that is, the debugger invoked with the DCL
    command DEBUG/KEEP) shares I/O channels with the parent process
    when it is run by a SPAWN/NOWAIT command. Therefore, in the VSI
    DECwindows Motif for OpenVMS user interface, you must press the
    Return key twice on the DECterm from which the debugger was run
    after the debugger version number has appeared in the command
    view.

    Optionally, you can execute the kept debugger in the following
    manner:

     $ DEFINE DBG$INPUT NL:
     $ SPAWN/NOWAIT RUN DEBUG/KEEP