Database fragmentation and allocation: An integrated methodology and case study

Distributed database design requires decisions on closely related issues such as fragmentation, allocation, degree of replication, concurrency control, and query processing. Integrated methodologies for distributed database design, therefore, tend to be very complex, predominantly theoretical, and limited in scope from a practical standpoint. Further, although the distribution options are interdependent, existing methodologies deal with fragmentation, replication, and allocation independent of one another. We develop an integrated methodology for fragmentation and allocation that is simple and practical and can be applied to real-life problems. The methodology also incorporates replication and concurrency control costs. At the same time, it is theoretically sound and comprehensive enough to achieve the objectives of efficiency and effectiveness. It distributes data across multiple sites such that design objectives in terms of response time and availability for transactions, and constraints on storage space, are adequately addressed. This work makes one of the first attempts at successfully combining fragmentation, allocation, and replication into a single step of distribution and applying the combination to a practical problem with positive results. This methodology has been used successfully in designing a distributed database system for a large geographically distributed organization.