VMS Help LANCP, DEFINE, DEVICE, Qualifiers, /UPDATE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Adds LAN devices that are not currently in the LAN permanent
    device database to that database. The initial entry for the
    device uses default values for all parameters. To update the
    permanent database with current information from the volatile
    database, use the DEFINE DEVICE command with the /VOLATILE_
    DATABASE qualifier. You can combine the /UPDATE and /VOLATILE_
    DATABASE qualifiers in a single DEFINE DEVICE command.