Oracle Real Application Clusters (RAC)

Oracle Real Application Clusters (RAC) is a database clustering technology that allows multiple instances of Oracle Database to run on separate servers while accessing a shared database. This setup provides high availability, scalability, and load balancing by distributing the workload across multiple servers.

Key Features of Oracle RAC:

• High Availability: Oracle RAC ensures that the database remains available even if one or more instances fail. This is achieved through features like Fast Application Notification (FAN) and Cache Fusion.
• Scalability: Oracle RAC allows the database to scale out by adding more servers to the cluster, which can handle more transactions and users.
• Load Balancing: Workloads are distributed across multiple instances, improving performance and resource utilization.
• Single System Image: From the perspective of applications and users, the cluster appears as a single system, even though it is composed of multiple interconnected servers.

How Oracle RAC Works:

• Interconnect: All instances in an Oracle RAC environment are connected through a high-speed interconnect, which allows them to share data and coordinate operations.
• Cache Fusion: This technology allows instances to share a single, global cache, ensuring data consistency and reducing the need for disk I/O.
• Oracle Clusterware: This infrastructure component manages the cluster, including resources like VIP addresses, databases, listeners, and services.

Oracle RAC is particularly useful for applications that require high availability and scalability, such as e-commerce websites, financial systems, and telecommunication systems.