9221947 Breitbart Transaction Management in a Heterogeneous Database Environment This is the first year of a three-year continuing award. A multidatabase system (MDBS) consists of a number of sites which run distinct commercial database management systems (DBMSs). The goal of an MDBS is to integrate the DBMSs, allowing applications to access data from, without requiring modifications to, the individual DBMSs. The autonomous user organizations in a multidatabase system generally have invested substantial capital in the DBMS and may, rightly, be unwilling to modify or lose control over their DBMSs. Therefore, it is imperative to develop multidatabase transaction processing methods that allow a high degree of local autonomy, but support users' data in a consistent and reliable manner. This research investigates how to manage and guarantee consistency of data residing in heterogeneous DBMSs, while adhering to the autonomy requirements of the participant DBMSs. The MDBS transaction management schemes developed in this research have the following characteristics: (1) adapt to MDBS environments, existing techniques for ensuring database consistency based on preserving transaction atomicity and serializability; (2) utilize alternate correctness criteria that relax the serializability and atomicity requirements. Pilot systems developed for both the serializability and the relaxed serializability models are used to conduct performance evaluation to ascertain that the developed schemes permit a high degree of concurrency. The results of the research will provide the basic transaction management mechanisms necessary for the development of a complete multidatabase management system. ***
