Stepwise Redesign of Distributed Relational Databases Y Stepwise Redesign of Distributed Relational Databases 2

Designing distributed databases is an issue of paramount importance for executing transactions eeciently. The distributed database design process consists of three phases namely, the initial design, redesign and materialization of the redesign. The initial design consists of a fragmentation and an allocation scheme which minimize the irrelevant data access cost and data transfer cost. Over a period of time there may be physical and logical changes which eeect the processing of transactions on a distributed relational database system. These changes necessitate redesign of the distributed databases in order to keep the performance of transactions from degrading. In this paper, we address the problem of stepwise redesign of distributed relational databases. A stepwise redesign is a process by which a new design is eeected in a dynamic processing environment by monitoring irrelevant data access and data transfer cost. Stepwise redesign of a distributed database consists of a split phase or/and merge phase. The split phase attempts to break a fragment into smaller fragments based on the transactions accessing diierent parts of the fragment. On the other hand, a merge phase attempts to construct a merged fragment from a set of fragments ac-cessed together by a set of transactions. We present experimental results to evaluate the eeectiveness and the utility of the stepwise redesign methodology.