Shared SCAN has been introduced primarily to reduce the number of IP-addresses required during cluster deployments. With a Shared SCAN VIP configured on one cluster (called the ‘Shared SCAN Cluster’), existing and new 18c and newer clusters can be configured to utilize this single SCAN VIP setup, rather than having themconfigured for each of these clusters (called‘Shared SCAN clients’)

A shared single client access name (SCAN) enables you to share one set of SCAN virtual IPs (VIPs) and listeners on a dedicated cluster with other clusters.

The use of a shared SCAN enables multiple clusters to use a single common set of SCAN virtual IP (VIP) addresses to manage user connections, instead of deploying a set of SCAN VIPs per cluster.

For example, instead of 10 clusters deploying 3 SCAN VIPs per cluster using a total of 30 IP addresses, with shared SCAN deployments, you only deploy 3 SCAN VIPs for those same 10 clusters, requiring only 3 IP addresses.

Simpler still, specify the Shared SCAN credential file during deployment:

Database clients (users) would connect to a specific database on a Shared SCAN client as they would to a database on a cluster with locally configured SCAN. Their connection string would specify the SCAN Name, the port and the service, exactly as they do with a local SCAN configuration. Note that it is the port and the service that differentiates the SCAN Listeners on the Shared SCAN Cluster.