Client connection requests are failing because the listener in not responding. You want to forward client connect request to another listener if one listener is not responding. How do you achieve this?

Connect-time failover is a client-side feature that automatically forwards connection requests to another listener if the primary listener fails to respond. This is configured in tnsnames.ora with the FAILOVER=ON parameter and multiple ADDRESS lists. Instance failover and TAF are different mechanisms for handling failures after connection is established.