<Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2007) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2007) (Learn how and when to remove this template message) </Td> </Tr> <P> Oracle Clusterware is the cross-platform cluster software required to run the Real Application Clusters (RAC) option for Oracle Database . It provides the basic clustering services at the operating - system level that enable Oracle Database software to run in clustering mode . In earlier versions of Oracle (release 9i and earlier), RAC required a vendor - supplied clusterware like Sun Cluster or Veritas Cluster Server (except when running on Linux or on Microsoft Windows). </P> <P> Oracle Clusterware is the software which enables the nodes to communicate with each other, allowing them to form the cluster of nodes which behaves as a single logical server . Oracle Clusterware is run by Cluster Ready Services (CRS) consisting of two key components: Oracle Cluster Registry (OCR), which records and maintains the cluster and node membership information; voting disk, which polls for consistent heartbeat information from all the nodes when the cluster is running, and acts as a tiebreaker during communication failures . </P>

What is the difference between oracle clusterware and rac
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