Oracle Client issue with TNS Listener when using EZconnect (ORA:12541)

Question

I have installed Oracle 11g , after that ODAC x64 and after that ODAC x86 (to get ODT) and successfully ran Oracle 11g and Oracle Data Provider x64 for my C# project that uses Oracle in backend.

I used EZconnect naming method to connect to the Oracle database. I followed some deployment instructions from Stackoverflow , whereby I copied 4 or 5 dlls into the directory of the executable as suggested.

Although the program on the target machine can detect the Oracle Data Provider as well as Oracle Client , it gives error ORA:12541 No TNS listener . Please help me resolve this issue.

Answer 1

The listener runs on the database server-- you need a listener in order to establish a connection to the database from any remote client. It is completely unrelated to the client configuration and how the client is configured to resolve a TNS alias.

Are you sure that the listener is running and that you're trying to connect to the proper machine on the proper port? The error implies that you're connecting to the wrong machine. that you're connecting on the wrong port, that you've specified the wrong service name, or that the listener for the database is down. The first three would be errors in the client configuration. The last one would mean that the problem is on the server.