RAC 11204 Client Connections Failing TNS-12514: Listener Does not know of service name

Hi all ...

In the process of performing a rolling patching on our 2-node 11204 RAC, there was a < 1 minute period where clients started getting this error message. I believe when the scan listener failed over, there was a period of time where it did not know of any of the services. When I examined the scan listener log, I can clearly see the TNS- errors after the listener started till about < 1 minute later, I saw the service registration messages and same failed connections started to succeed again.

Looking for ways to eliminate this scenario or minimize it. My research led me to multiple known bugs causing services not to register after a scan fail-over. One seems to apply on 11204 e.g. 21982225.