Oracle RAC Scan IP

 Scan IP:

In Oracle Real Application Clusters (RAC), SCAN stands for Single Client Access Name. It is a virtual IP address that provides a single name for clients to connect to the database service, regardless of the number of nodes or instances in the cluster. The SCAN IP simplifies client connectivity and load balancing in a RAC environment.

The SCAN IP is associated with the SCAN listener, which is a single listener process that runs on each node in the cluster. When a client connects to the SCAN IP, the SCAN listener routes the connection to one of the available nodes in the cluster, distributing the workload across multiple instances.

Here are some key points about SCAN IP in Oracle RAC:

1. Simplified Client Connectivity: Instead of specifying individual node addresses or instance names, clients can connect to the SCAN IP to access the RAC database. This simplifies the client configuration and eliminates the need to update client connection details when the cluster topology changes.

2. Load Balancing: The SCAN listener performs load balancing by distributing client connections across the available nodes. It uses a load-balancing algorithm to route each connection request to a different node, distributing the workload evenly across the cluster.

3. Transparent Node Addition/Removal: With the SCAN IP, adding or removing nodes from the cluster does not impact client connectivity. Clients continue to connect to the SCAN IP, and the SCAN listener automatically redirects the connections to the appropriate nodes, even if the cluster topology changes.

4. High Availability: The SCAN IP enhances high availability by providing a single, highly available entry point for client connections. If a node or SCAN listener fails, the SCAN VIP is automatically relocated to another node, ensuring continuous client connectivity.

5. SCAN VIP and SCAN Listener: The SCAN IP consists of a virtual IP address (SCAN VIP) and a corresponding SCAN listener. The SCAN VIP is assigned to one of the nodes in the cluster, and the SCAN listener runs on each node to handle client connections to the SCAN IP.

By using the SCAN IP in Oracle RAC, clients can connect to the database service seamlessly, without the need to manage individual node addresses. The SCAN IP provides a centralized and load-balanced access point to the RAC database, enhancing scalability, availability, and ease of client connectivity.