Library /sys$common/syshlp/tracehlp.hlb SPAWN, /WAIT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    /[NO]WAIT

    Controls whether the system waits until the current  subprocess  is
    completed  before allowing more commands to be issued in the parent
    process.  The /NOWAIT qualifier allows you to  issue  new  commands
    while  the  specified  subprocess  is  running.   When  you use the
    /NOWAIT  qualifier  interactively,  be  sure  to  use  the  /OUTPUT
    qualifier as well so that output from the subprocess is directed to
    a file rather than to your terminal.  Otherwise, your terminal will
    be used by more than one process at the same time.

    See the DCL help on SPAWN for further details.