Oracle Real Application Clusters (Oracle RAC) provides two service-based load balancing options - Connection Load Balancing (CLB) and Runtime Load Balancing (RLB). Load balancing enables fine-grained control over how client connections are distributed among instances within an Oracle RAC cluster.
- Connection Load Balancing (CLB): It balances incoming client connection requests among instances based on predefined rules and configurations. CLB works when a connection is established. When a client connects to the service, the listener selects an instance for the client based on predefined load balancing rules. It redirects client connections to Oracle RAC instances that are handling fewer connections.
- Runtime Load Balancing (RLB): It dynamically distributes the client connections at runtime based on the real-time metrics. RLB constantly monitors CPU utilization, response time, and other performance metrics of the Oracle RAC instance. Based on these performance metrics, RLB dynamically distributes new client connections to Oracle RAC instances that provide optimal performance. It ensures that the client connections are directed to the most suitable instances.
CLB and RLB are essential Oracle RAC features that offer advanced load balancing capabilities at both connection establishment and runtime levels. They improve system responsiveness, optimize resource utilization, and ensure high availability across the database cluster.