If the specified address is already in use by another host, no changes are made. If the specified hostname exists and has an address on the old subnet, the hostname is deleted from the database. Some network devices have more than one host name. An additional host name is called an alias name. Just like regular host names, an alias name must be unique in the ucdavis.edu domain.
Some network devices require a special DNS record to assist with e-mail delivery to their host name.
Both 'hostname' and 'exchanger' must be existing host names. In general, a host name should be about 8-12 characters long, without special characters. It is permissible to use host names shorter than 8 characters or longer than 12 characters. A formal, fully qualified host name will always end in 'ucdavis.edu'. There are many ways to come up with host names.