High Availability and Load Balancing in Oracle RAC
High Availability in Oracle RAC:
- Concept: Oracle RAC ensures continuous database availability by distributing workloads across multiple nodes. If one node fails, the remaining nodes continue to provide service.
- Failover: In case of failure, Oracle RAC provides failover capabilities where active sessions are transferred to another available node without user disruption.
- Redundancy: RAC uses redundant components like network interfaces, storage, and servers to minimize single points of failure.
- Automatic Reconfiguration: Oracle Clusterware automatically reconfigures the cluster when a failure occurs, helping in seamless availability.
- Rolling Patching: Patches can be applied to RAC nodes in a rolling fashion, ensuring that the database remains available during maintenance.
Load Balancing in Oracle RAC:
- Client-Side Load Balancing: Distributes incoming connections across all active nodes in the RAC cluster. Defined in the client’s TNSNAMES.ORA file or through the Oracle SCAN (Single Client Access Name) feature.
- Server-Side Load Balancing: Automatically balances the load of client connections across RAC instances. Oracle Net Services ensures that workloads are distributed based on server metrics like CPU usage and session load.
- SCAN (Single Client Access Name): Simplifies the management of client connections in RAC by providing a single network name for the cluster, which is load-balanced across all nodes.
- Service-Oriented Load Balancing: RAC services can be configured for specific workloads, distributing them across instances to optimize performance.
