Concurrency control mechanisms for multidatabase systems

Abstract

In conventional systems, transaction management has been thoroughly investigated and is now considered to be well understood. Transaction management in multidatabase systems, however, is less well understood. A multidatabase system (MDBS) is a type of distributed database system built from a collection of different centralized database systems (DBSs) located on sites in a computer network. The MDBS design goals differ from those of conventional DBSs in that a compromise is sought between the seemingly contradictory goals of creating a logically integrated database and allowing each component DBS to continue to function autonomously from the MDBS. The conventional concurrency control correctness criterion for a DBS is serializability. It is, however, not always possible to guarantee serializability in a MDBS using the conventional approach. Several seemingly different solutions have been proposed. Using the nested transaction paradigm we provide a simple model which is used to develop a number of new MDBS schedulers by applying existing theory and concepts. The utility of our model is further illustrated by using it as a framework for explaining and justifying existing solutions, including those with weaker correctness criteria.