VMS Help SHOW, SYSTEM, Qualifiers, /MULTITHREAD  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Displays all multithreaded processes for the local system.
    When used with the /FULL qualifier, the /MULTITHREAD qualifier
    displays information about each kernel thread in a multithreaded
    process.

    For more information on kernel threads, refer to the OpenVMS
    Programming Concepts Manual.