Each Oracle Java Cloud Service instance is comprised of several cloud services and middleware components. Each service instance has a single Oracle WebLogic Server domain that consists of one WebLogic Administration Server and a cluster of Managed Servers to host your Java application deployments. When Oracle Coherence is enabled for a service instance, there is a second cluster of Managed Servers that provide an in-memory data grid for your applications. Optionally, you can configure a load balancer, particularly if you have configured more than one Managed Server. This figure illustrates the components that make up a typical service instance: