I've got two RAC Systems connected by DataGuard.
When the primary site ist lost completly I will do an failover.
That's fine.
However, if primary comes up again, it has no idea about the failover.
It will therefore come up in open mode, I guess.
This will enbale clients to connect and write to the “former” primary and the current primary.
How to fix this?
Must I configure an observer to fix this problem?