Why do I get error "Client unable to establish connection: 'Failed to find host address 'myhost'" when using the Oracle ODBC driver?

Check the Server attribute in your ODBC data source specifies a valid machine name or IP address. Check that the machine name can be resolved using DNS lookup or is present in /etc/hosts. Check that you are on the same network as the target host by pinging the machine:

ping myhost

If ping times out or fails, either the DNS lookup is not working properly or there is some other networking or routing issue that needs to be resolved. Contact your network administrator.