Direct—A Multiprocessor Organization for Supporting Relational Database Management Systems

The design of DIRECT, a multiprocessor organization for supporting relational database management systems is presented. DIRECT has a multiple-instruction multiple-data stream (MIMD) 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, the type and number of relational algebra operations it contains, and the size of the relations referenced. Since DIRECT iS a virtual memory machine, the maximum relation size is not limited to that of the associative memory as in some other database machines. Concurrent updates are controlled through the use of locks on relations which are maintained by a controlling processor.