Components of Oracle RAC

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The three main components of Oracle RAC are described here.

Oracle RAC consist of three components:
The Oracle clusterware software (CRS)
Software to create and manages the communication between the cluster of nodes
The relational database (RDBMS)
The same relational database that can be installed as a stand-alone database
The Automatic Storage Manager (ASM)
A disk manager program that provides the capability to share data files stored on disk arrays.
Figure 1 illustrates these three components and their responsibilities.
Figure 1. Oracle RAC components
Oracle RAC components and their responsibilities. There are three Oracle RAC components. First is the RDBMS, which is a database created in Oracle with multiple instances on different servers. Each instance shares a common design and accesses the same data but has its own control files and logs. Second is the Clusterware CRS, which maintains cluster membership, a list of servers in the cluster at any moment in time. Also responsible for cache fusion - a unified cache for all cluster members. The third is Shared file system and disk management, which manages metadata and maintains file consistency of shared storage used for data accessed by RDBMS.