what is the difference between oracle clusterware and rac
Oracle Clusterware 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).