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

     Specifies that the system is not to wait until the subprocess is
     completed before allowing more commands to be specified.  This
     qualifier allows you to specify new commands while the spawned
     subprocess is running.  If you specify /NOWAIT, you should use
     /OUTPUT to direct the output of the subprocess to a file to prevent
     your terminal from being used by more than one process simultaneously.

     The default is that the system will wait until the subprocess is
     completed before allowing more commands to be specified.