CHAPTER 15
Extending Oracle RAC for Maximum Availability

As Real Application Clusters is becoming an increasingly common solution for scalability across enterprises, it is time to think beyond the obvious. Oracle RAC is designed primarily as a scalability and availability solution that resides in a single datacenter. However, it is possible, under certain circumstances, to build and deploy an Oracle RAC system in which the nodes in the cluster are locationally isolated by great distances. Having nodes in geographically separate locations provides continuous data availability and limited disaster recovery in case of site failures.

The choice of extending Oracle RAC depends on the failure it is designed to address. To protect against multiple points of failure, a cluster must be geographically dispersed: nodes can be put in different rooms, on different floors of a building, or even in separate buildings or separate cities. Your decision as to the distance between the nodes rests on the types of disaster from which you need protection and the technology used to replicate data between the storage systems.