ORA-12203 TNS:unable to connect to destination
Cause: Invalid TNS address supplied or destination is not listening. This error can also occur because of underlying network transport problems.
Action: Verify that the service name you entered on the command line was correct. Ensure that the listener is running at the remote node and that the ADDRESS parameters specified in TNSNAMES.ORA are correct. Finally, check that all Interchanges needed to make the connection are up and running.