What is the difference between Oracle Clusterware and Oracle Real Application Clusters?
In the event of a system failure, clustering ensures high availability to users. Redundant hardware components, such as additional nodes, interconnect, and disks, allow the cluster to provide high availability. Such redundant hardware architectures avoid single points-of-failure and provide exceptional fault resilience. In Oracle Real Application Clusters (RAC) environments, Oracle Clusterware monitors and manages Real Application Cluster databases. When a node in the cluster is started, all instances, listeners and services are automatically started. If an instance fails, the clusterware will automatically restart the instance, so that the service is often restored before the administrator notices it was down. In this sense Oracle Clusterware is the basis for Oracle Real Application Clusters. In those environments RAC ensures the continuous operation of the database as well as its scalability by running more than one database instance simultaneously, typically one on every node in the
