Why do I get error "Client unable to establish connection: ORA-12514, TNS:listener does not currently know of service requested in connect descriptor"; when using the Oracle ODBC driver?

Check that you've specified a valid service name with the SID attribute in odbc.ini.

If the service name is valid, it may be that the database service is not running or has not registered with the listener.

Failure to register with the listener may be a temporary condition. For example, the database may not have registered yet because the listener has only recently been started. It's therefore worth waiting a few moments and then reconnecting to your ODBC data source, before contacting your database administrator.