Oracle RAC

A cluster comprises multiple interconnected computers or servers that appear as if they are one server to end users and applications. Oracle RAC enables you to cluster Oracle databases. Oracle RAC uses Oracle Clusterware for the infrastructure to bind multiple servers so they operate as a single system.

Oracle Clusterware is a portable cluster management solution that is integrated with Oracle Database. Oracle Clusterware is also a required component for using Oracle RAC. Besides, Oracle Clusterware enables both single-instance Oracle databases and Oracle RAC databases to use the Oracle high-availability infrastructure. Oracle Clusterware enables you to create a clustered pool of storage to be used by any combination of single-instance and Oracle RAC databases.

Oracle Clusterware is the only clusterware that you need for most platforms on which Oracle RAC operates. You can also use clusterware from other vendors if the clusterware is certified for Oracle RAC.

In addition to the Oracle GoldenGate core platform for real-time data movement, Oracle provides the Management Pack for Oracle GoldenGate—a visual management and monitoring solution for Oracle GoldenGate deployments—as well as Oracle GoldenGate Veridata, which allows high-speed, high-volume comparison between two in-use databases.

Oracle Extended RAC

Oracle Database with Oracle RAC architecture is designed primarily as a scalability and availability solution that resides in a single data center. It is possible however, under certain circumstances, to build and deploy an Oracle RAC system where the nodes in the cluster are separated by up to 100 kilometers, to share the same RAC database with multiple RAC instances spread across two sites. This architecture is referred to as an Extended RAC or Metro cluster. We can consider this database architecture as an extension of Availability level 3.

The advantages of using Oracle RAC on extended clusters include:

An Oracle RAC Extended cluster is an architecture that provides extremely fast recovery from a site failure and allows for all nodes, at all sites, to actively process transactions as part of single database cluster. When two data centers are located relatively close to each other (Campus Cluster), extended clusters can provide great protection for some disasters, but not all. Fire, flooding, and site power failure are just a few examples of limited geographic disasters that can fail in an entire data center.