Oracle Solution for Error ora-12203

ORA-12203: TNS:unable to connect to destination

What triggered the Error:

Invalid address specified or destination is not listening. This error can also occur because of underlying network or network transport problems.

What should we do to fix it:

Verify that the net service name you entered was correct. Verify that the ADDRESS portion of the connect descriptor which corresponds to the net service name is correct. Ensure that the destination process (for example the listener) is running at the remote node.