SCAN Listeners and Service Registration Restriction With Valid Node Checking

You can use valid node checking to specify the nodes and subnets from which the SCAN listener accepts registrations. You can specify the nodes and subnet information using SRVCTL. SRVCTL stores the node and subnet information in the SCAN listener resource profile. The SCAN listener agent reads that information from the resource profile and writes it to the listener.ora file.

For non-cluster (single-instance) databases, the local listener accepts service registrations only from database instances on the local node. Oracle RAC releases before Oracle RAC 11g release 2 (11.2) do not use SCAN listeners, and attempt to register their services with the local listener and the listeners defined by the REMOTE_LISTENERS initialization parameter. To support service registration for these database instances, the default value of valid_node_check_for_registration_alias for the local listener in Oracle RAC 12c is set to the value SUBNET, rather than to the local node. To change the valid node checking settings for the node listeners, edit the listener.ora file.

SCAN listeners must accept service registration from instances on remote nodes. For SCAN listeners, the value of valid_node_check_for_registration_alias is set to SUBNET in the listener.ora file so that the corresponding listener can accept service registrations that originate from the same subnet.

You can configure the listeners to accept service registrations from a different subnet. For example, you might want to configure this environment when SCAN listeners share with instances on different clusters, and nodes in those clusters are on a different subnet. Run the srvctl modfiy scan_listener -invitednodes -invitedsubnets command to include the nodes in this environment.

You must also run the srvctl modify nodeapps -remoteservers host:port,... command to connect the Oracle Notification Service networks of this cluster and the cluster with the invited instances.