For an Oracle database, use the Oracle Net Configuration Assistant to configure a local net service name that points to the database server. You will also need to ensure that your Oracle Client is the correct version for the Oracle database server. Refer to the Oracle documentation for details on configuring local net service names.
If the Oracle database instance ever goes down, once it is restarted you must recycle the IIS application pools on the application server in order to restore their worker process connections to the database.
After installing the Oracle 64-bit client on the application server, the server should be rebooted.