Oracle RAC Components

The Oracle Database 11g RAC stack is slightly different from previous versions of Oracle because the clustering software is totally integrated into the RDBMS kernel in the latest version. In earlier versions of Oracle RAC the third-party vendors (except for Linux and Windows ports, where Oracle started shipping its own clusterware) provide the underlying clustering functionality. Starting from Oracle 11g Release 2, Oracle Clusterware stack is known as Oracle Grid Infrastructure.

The major components of Oracle RAC are

Shared disk system

Oracle Clusterware

Cluster interconnects

Oracle kernel components

Figure 3-2 shows the basic architecture.

FIGURE 3-2 Oracle 11g architecture

Shared Disk System

Scalable shared storage is a critical component of an Oracle RAC environment. Traditionally, storage was attached to each individual server using SCSI (Small Computer System Interface) or SATA (Serial ATA) interfaces local to the hosts. Today, more flexible storage is popular and is accessible over storage area networks (SANs) or network attached storage (NAS) using regular Ethernet networks. These new storage options enable multiple servers to access the same set of disks through a network, simplifying provisioning of storage in any distributed environment. SANs represent the evolution of data storage technology to this point.