What is an Extended Distance Oracle RAC Cluster?
As the name implies, an Extended Distance Cluster is a cluster, in which most or all the nodes are not local and typically set up with a certain distance between them. Clusters of this kind have been referred to by many names, including “campus clusters”, “metro clusters”, “geo clusters”, “stretched clusters” and “extended clusters”. Some of these names imply a vague notion of distance range.
This type of configuration will be referred to as either Oracle RAC on “Extended Distance Clusters” or “Stretched Clusters”, while the names will be used synonymous.
If Oracle RAC One Node is concerned in a certain context, respective references will be made.
Unlike classic Oracle RAC implementations, which are primarily designed as scalability and high availability solution that resides in a single data center, it is possible – under certain circumstances – to build and deploy an Oracle RAC system in which the nodes are separated by greater distances.
For example, if a customer has a corporate campus, they might want to place the individual Oracle RAC nodes in separate buildings. This configuration provides a higher degree of disaster tolerance, in addition to the normal Oracle RAC high availability, since a fire in one building would not, if properly set up, stop the database from processing. Similar, many customers have two data centers in reasonable proximity.