FTP performs fast file transfers between two OpenVMS systems by
    using VMS Plus Mode.

    When FTP identifies file transfers between two OpenVMS hosts
    running TCP/IP Services, it transfers files in large blocks
    rather than in small records. VMS Plus Mode greatly increases
    the transfer speed and preserves all Record Management Services
    (RMS) file attributes.

    FTP automatically disables VMS Plus Mode when your session is
    with a UNIX host or with an OpenVMS host not running TCP/IP
    Services.