Library /sys$common/syshlp/latcp$help.hlb ATTACH, Qualifier, /PID  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /PID=pid

    Specifies the process identification (PID) of the process that
    will have terminal control. When you specify a PID, you can omit
    the leading zeros. If you specify a PID, do not use the process
    name parameter. If you omit the PID qualifier, you must use the
    process name parameter.