It’s usual to use DNS Aliases pointing to scanlistener. This way, we create an abstraction/layer bewteen clients/application and the cluster where database is. Some activities like tierization/consolidation and database moving between clusters (converting to Pluggable, etc), would be much more transparent.
Buuuut, if after a database migration, all the services online and listening, your client is stucking with:
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor
Remmember you are using DNS to make this layer. Have you tried to flush DNS Cache?
I faced this problem with a Windows Application. The solution:
C:\Users\matheus_boesing>ipconfig /flushdns Windows IP Configuration Successfully flushed the DNS Resolver Cache.
All working fine after that. 🙂