/SECONDARY=([NO]DOMAIN:do,[NO]FILE:file,[NO]HOST:host)

    Optional. Default: None.

    Specifies the secondary server for the specified zone. Multiple
    secondary servers are allowed if each is associated with a
    different domain.

    o  DOMAIN keys to a particular record within a type.

       NODOMAIN deletes the entry.

    o  FILE specifies the name of the boot file.

       If you do not specify a file, the default file name is created
       from the value that you supply with the DOMAIN option.

       NOFILE specifies that no file is created.

    o  HOST is a list of hosts from which the secondary server copies
       the database file.

       NOHOST deletes hosts from the host list.