VMS Help SET, DEVICE, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 device-name[:]

    Specifies the name of the device whose spooling or operational
    status is to change. The device must be a print device or a
    terminal if you want to change the spooling status; the device
    must be a disk or magnetic tape if you want to change the
    operational status.