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The design of DIRECT, a multiprocessor organization for supporting relational data base management systems is presented. DIRECT has a MIMD (multiple instruction stream, multiple data stream) architecture. It can simultaneously support both intra-query and inter-query concurrency. The number of processors assigned to a query is dynamically determined by the priority of the query and the size of the relations it references. The size of a relation is not limited to that of the associative memory as in some previous data base machines. Concurrent updates are controlled through address translation tables which are maintained by a controlling processor.
David J. DeWitt (Sun,) studied this question.