My replay was quite right, how u can say without try or apply..... below i m showing the example with error and solution.... please read carefully and do not say again to me and others......
--- Now i showed you Edstevens, by above method my problem have resolved, and i solved this type of problem more than 100 times...
one point more is that when your database base is in idle state then without entry in the listener.ora file you can not connect to your database using connection string and face the 12514 error.
Only one problem with that .... you were solving the wrong problem.
You solved "ORA-12514: TNS:listener does not currently know of service requested in connect".
The OP is dealing with "ORA-12154: TNS:could not resolve the connect identifier specified".