Public network addresses are used to provide services to clients. If your clients are connecting to the Single Client Access Name (SCAN) addresses, then you may need to change public and virtual IP addresses as you add or remove nodes from the cluster, but you do not need to update clients with new cluster addresses.
Note:
You can edit the listener.ora file to make modifications to the Oracle Net listener parameters for SCAN and the node listener. For example, you can set TRACE_LEVEL_listener_name. However, you cannot set protocol address parameters to define listening endpoints, because the listener agent dynamically manages them.
See Also:
Oracle Database Net Services Reference for more information about the editing the listener.ora file
SCANs function like a cluster alias. However, SCANs are resolved on any node in the cluster, so unlike a VIP address for a node, clients connecting to the SCAN no longer require updated VIP addresses as nodes are added to or removed from the cluster. Because the SCAN addresses resolve to the cluster, rather than to a node address in the cluster, nodes can be added to or removed from the cluster without affecting the SCAN address configuration.
The SCAN is a fully qualified name (host name and ___domain) that is configured to resolve to all the addresses allocated for the SCAN. The SCAN resolves to one of the three addresses configured for the SCAN name on the DNS server, or resolves within the cluster in a GNS configuration. SCAN listeners can run on any node in the cluster. SCANs provide ___location independence for the databases, so that client configuration does not have to depend on which nodes run a particular database.
Oracle Database 11g release 2 (11.2), and later, instances only register with SCAN listeners as remote listeners. Upgraded databases register with SCAN listeners as remote listeners, and also continue to register with all node listeners.
Note:
Because of the Oracle Clusterware installation requirement that you provide a SCAN name during installation, if you resolved at least one IP address using the server /etc/hosts file to bypass the installation requirement but you do not have the infrastructure required for SCAN, then, after the installation, you can ignore the SCAN and connect to the databases in the cluster using VIPs.
Oracle does not support removing the SCAN address.