Creating service in Oracle RAC

To reduce the Oracle cluster overhead you may want your application or some of module of your application to connect only with some specific set of nodes while maintain connection fail-over the high availability feature  at the same time. This can be achieved by creating RAC specific service. Say you have 4 instance RAC database but you want your sales module to connect to database only to Instance 1 and Instance 2. I've made a video for creating service in Oracle RAC to connect applications to specific node(or set of nodes), called preferable instances  nodes and fail-over to other instances nodes . It is very simple without dbca(not in dbca from 11g)