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

       /WAIT (default)
       /NOWAIT

    Requires that you wait for the subprocess to terminate before
    you enter another DCL command. The /NOWAIT qualifier allows you
    to enter new commands while the subprocess is running. (Use the
    /OUTPUT qualifier with the /NOWAIT qualifier to avoid displaying
    both parent and subprocess output on the terminal simultaneously.)