What is Oracle scan_listener?
A listener acts as a bridge between the instance and client processes, and this connection is established through a registration process. During registration, the instance informs the listener of its database instance name (instance_name) and service names (service_names). The listener uses this registered information to route client requests to the correct service instance.
Currently, Oracle provides two methods for registration: dynamic registration and static registration. Client connections are made directly to the instance's IP address, meaning that the load balancing feature provided by scan_ip is only used during the initial connection phase. Subsequent interactions between the client and server do not involve scan_ip.
This explanation is reasonable; otherwise, during failover, the connection between the client and server would not be maintained and would require a new handshake and authentication.
Failover is a critical functionality of RAC's fault tolerance. It automatically redirects requests to other available instances when a database instance crashes, providing a high degree of availability. In this process, detecting the instance failure and redirecting requests to another instance is the responsibility of the listener
