How can I add more SCAN VIPs or listeners not using DNS?
You can only create the 3 SCAN VIPs and 3 SCAN Listeners across the cluster, if you have a DNS alias either at installation time or later. You need to resolve the SCAN Name to those formerly mentioned 3 IP addresses at the moment of creation or when modifying the SCAN. This is how they get created – the IPs that are resolved by the SCAN DNS entry are read and the respective VIPs get created. IF you have no DNS at all at hand at any time, especially not for the servers in your cluster, you will not get 3 SCAN VIPs in your cluster and hence you will have only 1 VIP, which can be considered a single point of failure. This means that you have 2 choices: You can either live with this configuration and the respective consequences OR you can fall back to using the nodes VIPs of the cluster to connect your clients to, neither of which is recommended, as mentioned in My Oracle Support note with DOC-Id. 887522.1 for example.
