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.

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Direct&#8212;A Multiprocessor Organization for Supporting Relational Database Management Systems

It is no accident that the set of mental and physical processes used by a designer working in a particular medium is called a design discipline. Something about the human mind tends to define a design medium in terms of its constraints, its limits. From the writing of haiku* to the design of new computers, designers tend to think in terms of a limiting structural framework to which their design must adhere. Consequently, when evolving style or advancing technology removes some of these constraints, designers often react with as much consternation as joy. The discipline ofcomputer architecture is now in such a transitional period. The advent of VLSI and very recently developed automated design tools have removed a fundamental constraint from computer architecture. Computer designers are no longer rigidly bound by the cost of processing logic. An obvious result is that the von Neumann paradigm for computer design, in which a single CPU operates serially on data items that it serially fetches from and restores to memory, is obsolete for computationally demanding tasks. The designer can now attack problems that once were computationally intractable by implementing systems in which thousands or even tens of thousands of processors cooperate to solve a single problem. A highly parallel structure has three main characteristics:

A survey of highly parallel computing

Design considerations of a database computer are presented in this paper. The overall architecture of the computer as well as the organization of its individual components are discussed. Several key concepts which are vital to database management are incorporated in the design and organization of the components. The concepts of tracks-in-parallel read-out and logic-per-some-track processing are provided in an on-line database store for the purpose of achieving high-volume content-addressability. The use of auxiliary information about the database for access precision and control has resulted in the design of a structure memory, an array of content-addressable memory and processor pairs, for large collections of indices. The choice of technologies for the implementation of these components is considered in terms of their cost and performance. Modified moving-head disk technology is chosen in order to support the very large on-line database store. Emerging technologies such as magnetic bubbles and CCD's are chosen for the structure memory on the basis of their matching performance with the on-line database store and their capability for parallel-in-blocks-and-serial-within-block processing. Five other important components are also disdissed in the paper. Their role in the database computer and relationship with the structure memory and on-line database store are delineated.

DBC&#8212;A Database Computer for Very Large Databases

Over a dozen relational database systems have been implemented since E. F. Codd introduced the relational model of data in a series of pioneering papers between 1970 and 1971 [CODD70, CODD71a, CODD71b, CODD71c]. A number of prototype systems (such as MIT's MADAM, GMR's RDMS, IBM's SEQUEL) were implemented primarily to demonstrate the feasibility of supporting high-level, nonprocedural data languages based on the relational algebra or the relational calculus. At about the same time, a number of other prototype systems {such as IBM's RM/XRM, GAMMA-0, and University of Toronto's ZETA/MINIZ) were developed for use as low-level, database access and storage subsystems for implementing high-level, nonprocedural, relational data languages. More recently, efforts have been directed toward implementing more comprehensive systems

Relational Database Systemsr

The architectural characteristics and the implementation techniques of a context addressed segment sequential memory system called CASSM are described. The system provides hardware support for many database management functions. It offers associative and parallel processing capabilities for the efficient retrieval and manipulation of data in large databases. The hardware is designed mainly to support a hierarchical model for database applications but also contains facilities for supporting a wide range of data searches and operations useful for other nonnumeric data processing applications. The software development of the assembly language CASAL and its assembler, the high-level nonprocedural language CASDAL and its compiler, the interface to the CASSM-user interface computer, etc., have been carried out for the system. The hardware design and implementation techniques have been verified using a one-cell prototype system and a simulator designed for testing the system in the multicell environment. The emphasis of this paper is in the detailed description of the hardware features and techniques used in the multicell CASSM system.

The Architectural Features and Implementation Techniques of the Multicell CASSM

Recent developments in storage technologies have given computer system designers a wide range to consider in building large on-line systems. It is important that the requirements of each component of a proposed system be carefully recognized before choosing a particular technology for its implementation. The design of a database computer which takes advantage of emerging technologies has been proposed. In this paper, the design of an important component of the database computer, namely, the structure memory, is described. Three design alternatives using three different technologies are proposed. These are magnetic bubble memories, charge-coupled devices, and electron beam addressable memories. The relationship of the structure memory with other components of the database computer is briefly outlined.

Structure memory designs for a database computer

: The database computer (DBC) is a specialized back-end computer which is capable of managing data of 10 to the 9th power -10 to the 10th power bytes in size and supporting known data models such as relational, network, hierarchical and attribute-based models. In addition to its intended purpose of handling large databases and interfacing with various data models, the DBC is one of the first database machines which have built-in protection mechanisms for access control and clustering mechanisms for performance enhancement.

The Architecture of a Database Computer. Part II. The Design of Structure Memory and its Related Processors.

: This is the last of the three-part series which deals with the design of a back-end computer known as the database computer (DBC). The concepts and capabilities of the DBC were presented in Part I. Schematically, the DBC architecture consists of two loops of memories and processors, namely, the structure loop and the data loop. The structure loop is composed of four components: the structure transformation unit (KXU), the structure memory (SM), the structure memory information processor (SMIP) and the index translation unit (IXU). The design philosophy, implementation details and hardware organizations of the structure loop components were documented in Part 2. In this report, the design of the data loop is presented. In addition, the database command and control processor (DBCCP), which regulates the operations of both the structure and data loops and interfaces with the front-end computer systems, is also presented. The DBCCP processes all DBC commands received from the front-end computer systems, schedules the execution of the commands on the basis of the command type and priority, enforces security on a selective basis, clusters records to be stored in the DBC and routes the response set to the front-end computer systems.

The Architecture of a Database Computer. Part III. The Design of the Mass Memory and Its Related Components.

: A hardware architecture for a database computer (DBC) is given in this paper. The proposed design overcomes many of the traditional problems of database system software and is one of the first to describe a complete data-secure computer capable of handling large databases.

The Architecture of a Database Computer. Part I. Concepts and Capabilities.

The design of a microprogrammable microprocessor-based keyword transformation unit for a database computer(DBC) is described. The DBC, a specialized back-end computer capable of managing 109 - 1010 bytes of data, consists of two loops of memories and processors, the structure loop and the data loop, connected through a database command and control processor (DBCCP).The structure loop is used to retrieve and update the large amount (107 - 109 bytes) of structural information about the database from a structure memory (SM) at a rate commensurate with the database operations performed on the mass memory of the data loop. A keyword transformation unit (KXU) is therefore required to enhance the performance of the structure memory. The KXU encodes variable-length keywords into a fixed-length form by hashing. By managing a library of carefully designed hashing algorithms and by dynamically loading the algorithms in a writable control store for execution, the KXU allows the efficient storage of keywords and their associated information and minimizes subsequent accesses to the SM.

Krishnamurthi Kannan

Papers

Structure memory designs for a database computer

The Architecture of a Database Computer. Part II. The Design of Structure Memory and its Related Processors.

The Architecture of a Database Computer. Part III. The Design of the Mass Memory and Its Related Components.

The Architecture of a Database Computer. Part I. Concepts and Capabilities.

A microprogrammed keyword transformation unit for a database computer