Chapter 1. Introduction

Abstract

There has been a continuing increase in the amount of data handled by database management systems (DBMSs) in recent years. Indeed, it is no longer unusual for a DBMS to manage databases ranging in size from hundreds of gigabytes to terabytes. This massive increase in database sizes is coupled with a growing need for DBMSs to exhibit more sophisticated functionality such as the support of object-oriented, deductive, and multimediabased applications. In many cases, these new requirements have rendered existing DBMSs unable to provide the necessary system performance, especially given that many mainframe DBMSs already have difficulty meeting the I/O and CPU performance requirements of traditional information systems that service large numbers of concurrent users and/or handle massive amounts of data [13]. To achieve the required performance levels, database systems have been increasingly required to make use of parallelism. As noted in [1], the traditional approach to parallelism for conventional DBMSs which use industry-standard database models such as the relational, can take one of two forms. The first is through the use of massively parallel general-purpose hardware platforms. As an example of this, commercial platforms such as nCube and SP1 are now supporting Oracle's parallel server [5]. Also, the Distributed Array Processor marketed by Cambridge Parallel Processing is now being used to produce a commercial massively parallel database system [4]. The second approach makes use of arrays of off-the-shelf components to form custom massively parallel systems. For the most part, these hardware systems are based onMIMD parallel architectures. The NCR 3700 [1] and the Super Database Computer II (SDC-II) [27] are two such systems. The NCR 3700 uses a high-performance multistage interconnection network known as Bynet and RAIDS (Redundant Arrays of Inexpensive Disks [11]). This system can now run a parallel version of Sybase relational DBMS [5, 26]. The SDC-II consists of eight data processing modules, where each module is composed of seven processors and five disk drives. The data processing modules communicate through an omega interconnection network.