VMS Help DTM, ATTACH, Command Qualifiers, /IDENTIFICATION  *Conan The Librarian (sorry for the slow response - running on an old VAX)

   /IDENTIFICATION=pid

   Specifies the process identification (PID) of the process to which
   you want to attach your terminal. You can omit the leading zeros
   when you specify a PID.

   If you specify the /IDENTIFICATION qualifier, do not specify the
   process name parameter or the /PARENT qualifier. If you do not
   specify a qualifier, you must specify a process name.