The figure shows requests going through a load balancer and into only one Oracle Application Server instance, I1, because the second instance I2 is stopped. Instance I1 is still in a cluster, Cluster1, but the second instance I2 is stopped and removed from Cluster1.
Each instance contains an OC4J instance called OC4J_Clustered. Version 0 of an application called "App" is running in OC4J_Clustered in I1. The two OC4J_Clustered instances are still in the same IP multicast replication group, but because I2 is stopped, HttpSession replication is not taking place.