Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 6 - Install, Configure and Database Creation

Cluster Software

As noted in figure 6.2, Oracle provides the clusterware for Windows 2000 and Linux clusters. Please note that throughout the book, when we refer to 'OSD', we mean the cluster related operating dependent system layer. The HA framework supplied by the vendors is not needed for a RAC environment. Instead of using the HA software, Oracle uses its own cluster software or an OSD supplied by the vendor to control the cluster lock management. Clustering software monitors and manages the cluster components that includes the servers and the server connections. The cluster software specializes in detecting failures through software probes, fault isolation, and fault containment, wherever applicable.

Usually the failure detection process involves determining the fault and applying the response. It could result in either switching over to a secondary component or the total shutdown of that component, in which case some kind of reconfiguration takes place. As an example, if two interconnects are configured, the fault or loss of one would not cripple the cluster, but would merely result in shutting it off. Whereas, when one of the nodes hangs, the cluster manager evicts the failed node and informs other members so that the application (database instance) can take the necessary reconfiguration action.

The cluster manager is also responsible for node monitoring, which includes polling the status of various resources like interconnect hardware/software, shared disks, Oracle instances, and public networks. The cluster manager interacts with the global cache service in RAC to reconfigure the failed instance resources.