Oracle Real Application Clusters (RAC) is a feature of Oracle Database that allows multiple instances to access a single physical database, thereby providing a highly available and scalable database solution. Some of the key features of RAC that enhance database availability and scalability include:
1. Clustered Architecture: RAC enables the database to be deployed in a clustered environment, where multiple servers are connected via a high-speed interconnect. This architecture provides high availability and scalability by allowing multiple instances to access the same database concurrently.
2. Shared Cache: RAC allows all nodes in the cluster to share the same database buffer cache. This enables data to be accessed more quickly, and results in improved performance and scalability.
3. Automatic Workload Management: RAC uses Automatic Workload Management (AWM) to balance the workload across all instances in the cluster. AWM dynamically adjusts database and application resources to ensure high performance and availability.
4. Online Patching: RAC enables patching and upgrades to be performed on individual nodes while the system remains online. This minimizes downtime and increases availability.
5. Oracle Global Data Services: Oracle Global Data Services (GDS) provides a single, unified view of databases configured in a RAC environment. GDS enables load balancing and failover across multiple databases, providing increased availability and scalability.
6. Load Balancing: RAC provides built-in load balancing for applications accessing the database. This ensures that requests are evenly distributed across all nodes in the cluster, preventing overloading of individual nodes.
7. Transparent Application Failover: RAC enables transparent application failover in the event of a node failure or other issue. This feature ensures that application connections are automatically redirected to available nodes, providing high availability and minimizing downtime.
Overall, Oracle Real Application Clusters provides a highly available and scalable database solution that can be deployed in a variety of configurations to meet the needs of any organization.