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Cluster Software

Oracle RAC Cluster Tips by Burleson Consulting

This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters.  To get immediate access to the code depot of working RAC scripts, buy it directly from the publisher and save more than 30%.

Once the nodes are physically interconnected, with either a cable or switch, plan to install the necessary cluster software on all the nodes. The clusterware installation method differs from vendor to vendor and from platform to platform.

Cluster software is usually referred to as cluster manager or operating system dependent layer (OSD) and is provided by the hardware vendor. The notable exceptions are Linux and Windows. For example, the following Table 6.2 shows the cluster software products that are available for setting up a RAC system.




Sun Cluster 3.1


Veritas Storage Foundation DBE/AC


Fujitsu-Siemens PrimeCluster


MC Service Guard and Veritas Storage Foundation

HP Tru64

Tru64 TruCluster


Oracle Supplied Clusterware (CRS)


Oracle Supplied Clusterware (CRS)

AIX pSeries


Table 6.2: Cluster Software (OSD)

As noted in Table 6.2, Oracle provides the clusterware for Windows 2000 and Linux clusters. Please note that throughout the book, when referring to OSD, it means 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 include 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 or 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.

Cluster software protects against the conditions of split-brain and amnesia. Split-brain condition occurs when communication between nodes is lost and the cluster becomes partitioned into sub-clusters, each believing that it is the only partition. Amnesia occurs when the cluster restarts after a shutdown using cluster configuration data older than at the time of the shutdown. The changes in cluster membership drive the cluster reconfiguration sequence that may, in turn, result in services being migrated from failed or faulty nodes to healthy ones.


This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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