Oracle RAC is ideal for data warehouse applications because it augments the noncluster benefits of Oracle Database. Oracle RAC does this by maximizing the processing available on all of the nodes that belong to an Oracle RAC database to provide speed-up for data warehouse systems.
The query optimizer considers parallel execution when determining the optimal execution plans. The default cost model for the query optimizer is CPU+I/O and the cost unit is time. In Oracle RAC, the query optimizer dynamically computes intelligent defaults for parallelism based on the number of processors in the nodes of the cluster. An evaluation of the costs of alternative access paths, table scans versus indexed access, for example, takes into account the degree of parallelism available for the operation. This results in Oracle Database selecting the execution plans that are optimized for your Oracle RAC configuration.