The shared memory architecture has zero communication cost : data and messages are
exchanged through the shared memory area. Advantages ofsuch an architecture include easier
process synchronization and minimal overhead for load balancing correction. But this
architecture can be scaled effectively up to 40 processors. Beyond that interference affectsthe
rate at which memory is processed.
The shared-nothing architecture is currently the more popular implementation, mainly due
to its high reliability and ease of scalability to hundreds of processors. It is also the most cost
effective means of constructing a parallel database system as it can be built from existing
sequential machines using a simple interconnection network [3].