Each node may have its own Oracle instance, with all the standard facilities of an instance. As with loosely coupled systems, cache consistency on MPPs must still be maintained across all nodes in the system. Thus, the overhead for cache management is still present. System growth is practically unlimited. MPPs are good for read-only databases and decision support applications.
More coordination is required.
More overhead is required for a process to work on a disk belonging to another node. If there is a heavy workload of updates or inserts, as in an online transaction processing system, it may be worthwhile to consider data-dependent routing to alleviate contention. Here, two shared disk systems are linked to form a system with the same hardware redundancies as a shared nothing system. If one CPU fails, the other CPUs can still access all disks. All Rights Reserved.