Can the hostname and IP address for the database tier be changed?

For the database, you need to look at the tnsnames.ora, listener.ora and sqlnet.ora files, and make changes as needed (IP, Hostname, etc.). DBConsole uses a WEB URL that also includes either the hostname or IP address. Other than that, nothing else is be needed for the database. As with any change like this, it is recommended you make a good back up and then test it on another server before putting it into production.