ORACLE -RAC (Real Application Clusters )

RAC COMPONENTS

The major components of a Oracle RAC system are

• • Shared disk system (SAN and NAS disk storage systems)

  • Oracle Clusterware

  • Cluster Interconnects

  • Oracle Kernel Components

  • Shared disk system :> Once you have you storage attached to the servers, you have three choices on how to setup the disks

  • Raw Volumes – normally used for performance benefits, however they are hard to manage and backup

  • Cluster FileSystem – used to hold all the Oracle data files can be used by windows and linux, its not used widely

  • AUTOMATIC STORAGE MANAGEMENT (ASM) – Oracle choice of storage management, its a portable, dedicated and optimized cluster filesystem

• • Oracle Clusterware :-> Oracle Clusterware software is designed to run Oracle in a cluster mode, it can support you to 64 nodes, 

  • Clusterware software allows nodes to communicate with each other and forms the cluster that makes the nodes work as a single logical server. The software is run by the Cluster Ready Services (CRS) using the Oracle Cluster Registry (OCR)

    • CRS has four components

    • OPROCd – Process Monitor Daemon

    • CRSd – CRS daemon, the failure of this daemon results in a node being reboot to avoid data corruption

    • OCSSd – Oracle Cluster Synchronization Service Daemon (updates the registry)

    • EVMd – Event Volume Manager Daemon