In the shared-memory architecture, the entire memory, i.e., main memory and disks, is shared by all processors. A special, fast interconnection network (e.g., a high-speed bus or a cross-bar switch) allows any processor to access any part of the memory in parallel. All processors are under the control of a single operating system which makes it easy to deal with load balancing. It is also very efficient since processors can communicate via the main memory.
Shared-memory is the architectural model adopted by recent servers based on symmetric multiprocessors (SMP). It has been used by several parallel database system prototypes and products as it makes DBMS porting easy, using both inter-query and intra-query parallelism.
Shared-memory has two advantages: simplicity and load balancing. Since directory and control information (e.g., lock tables) are shared by all processors, writing database software is not very different than for...