The key to performance in a decision support system is properly tuned queries and proper use of indexes, clusters, and hashing. By dividing the work necessary to process a statement among multiple server processes, the Oracle Server can process the statement more quickly than if only a single server process processed it. Figure  5-3 illustrates the parallel execution feature of the Oracle Server. Parallel execution helps system performance scale when adding hardware resources. If your system's CPUs and disk controllers are already heavily loaded, you need to alleviate the system's load before using parallel execution to improve performance.
Concepts provides general information about parallel execution.
Many applications rely on several configurations and Oracle options. You must decide what type of activity your application performs and determine which features are best suited for it. One typical multipurpose configuration is a combination of OLTP and data warehousing systems. Figure  5-4 illustrates multiple configurations and applications accessing an Oracle Server. The retail stores gather a large amount of data from daily purchases, and the marketing staff queries this data to determine which items sell best in which locations.