This diagram uses a simplified topology to show how primary and secondary regions reverse roles after a switchover and how the domain name system (DNS) directs clients to the new primary without changing the component topology.

Each region contains a single virtual cloud network (VCN). The VCN includes an OCI Load Balancer instance that accepts client requests resolved by the DNS. The load balancer forwards requests to application servers which use an instance of Oracle Database. The VCN also includes a dynamic routing gateway (DRG) to connect to the VCN in the peered region. Oracle Data Guard is used to synchonize the instances.