It reduces connectivity time for application or web based end users. Normally 3 SCANs are capable enough to handle hundreds of new connections in a span of few seconds. Still if you feel that default 3 SCAN listeners are not enough for your environment then you have an option to add few more scan listeners.

Why does Oracle RAC have 3 scan listeners?

As we know that the recommended value for SCAN ip using DNS/GNS is 3 SCAN IPS and this creates 3 SCan listeners randomly on the nodes. If we have a 5 node cluster then how many SCAN IPs are recommended.

What are scan listeners?

SCAN works by replacing a hostname or IP list with virtual IP addresses (VIP). ... Unlike a regular listener where the listener is accessed via a DNS hostname or IP address, a SCAN listener uses a list of domain names, allowing Oracle to assign incoming connections to a server using their own least-recently-used algorithm.