Computer Sciences Dept.

Direct - A Distributed Computer Architecture for Supporting Relational Data Base Management Systems

David DeWitt

The design of DIRECT, a distributed computer architecture 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. DIRECT is being implemented using LSI-11/03 microprocessors and CCD memories which are searched in an associative manner. A novel cross-point switch is used to connect the LSI-11 processors to the CCD memories. While cross-point switches have proven too expensive for use in general purpose parallel. processors, their application in DIRECT demonstrates that these switches can be successfully used in specialized applications.

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