Oracle DBA

Oracle 19c RAC (Real Application Clusters) is a high-availability and scalability solution provided by Oracle for Oracle Database. RAC allows multiple instances (database servers) to concurrently access a shared set of database files, providing a clustered database environment. It enables workload distribution, failover protection, and improved performance.

Key features of Oracle 19c RAC include:

1. Shared Storage: RAC uses a shared storage solution, such as a Storage Area Network (SAN) or Network-Attached Storage (NAS), to store the database files (data files, control files, and redo log files). This shared storage allows all instances in the cluster to access and modify the same database files simultaneously.
2. Scalability: RAC provides horizontal scalability by allowing additional instances to be added to the cluster, thereby increasing the processing power and capacity of the database. It allows workload distribution across multiple nodes, enabling better utilization of available resources.
3. High Availability: RAC enhances the availability of the database by providing automatic failover and load balancing capabilities. If one instance or node fails, the workload is automatically transferred to another available node, ensuring continuous access to the database with minimal downtime.
4. Load Balancing: RAC distributes database connections across multiple instances, improving performance by balancing the workload. The workload can be evenly distributed based on various load balancing algorithms, such as round-robin or service-based load balancing.
5. Cache Fusion: RAC utilizes a technology called Cache Fusion, which allows data blocks to be shared in the memory caches of multiple instances. This eliminates the need for inter-instance communication for block transfers, improving performance and reducing contention.
6. Clusterware: Oracle Clusterware is a key component of RAC that provides the infrastructure for managing the cluster and resources. It handles the coordination, monitoring, and management of the cluster nodes, ensuring high availability and cluster integrity.
7. Automatic Storage Management (ASM): ASM is a storage management solution specifically designed for Oracle databases. It simplifies storage administration by providing a file system and volume manager functionality optimized for Oracle databases. ASM is commonly used with RAC to manage the shared storage.

Oracle 19c RAC is widely used in environments that require high availability, scalability, and performance. It is particularly suitable for mission-critical applications, where uninterrupted access to the database is crucial. RAC provides the ability to scale resources as the workload grows and ensures database availability in the event of failures.