Single Client Access Name (SCAN) concept was first introduced in Oracle 11g Release 2 is a feature used in Oracle Real Application Cluster environments that provides a single connection name for clients. By using SCAN you don’t need to keep all cluster node entries in client’s tnsnames.ora file. Instead you use single SCAN address or hostname to access any Oracle Database running in a cluster by making it more dynamic. In other words, SCAN is an alias for databases in the cluster. The main purpose is that the client’s connect information does not needs to be changed if you add to or remove nodes from cluster. New terms such as SCAN Name, SCAN VIP, SCAN Listener, Node VIP comes with this feature and sometimes makes it complicated for new DBA’s.
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