Overcoming heterogeneity and autonomy in multidatabase systems

A multidatabase system (MDBS) is a software system for integration of preexisting and independent local database management systems (DBMSs). The transaction management problem in MDBSs consists of designing appropriate software, on top of local DBMSs. such that users can execute transactions that span multiple local DBMSs without jeopardizing database consistency. The difficulty in transaction management in MDBSs arises due to the heterogeneity of the transaction management algorithms used by the local DBMSs, and the desire to preserve their local autonomy. In this paper, we develop a framework for designing fault-tolerant transaction management algorithms for MDBS environments that effectively overcomes the heterogeneity- and autonomy-induced problems. The developed framework builds on our previous work. It uses the approach described in S. Mehrotra et al. (1992, in ``Proceedings of ACM-SIGMOD 1992 International Conference on Management of Data, San Diego, CA{''}) to overcome the problems in ensuring serializability that arise due to due to heterogeneity of the local concurrency control protocols. Furthermore, it uses a redo approach to recovery fur ensuring transaction atomicity (Y. Breitbart et al., 1990, in ``Proceedings of ACM-SIGMOD 1990 International Conference on Management of Data, Atlantic City, NJ;{''} Mehrotra et al., 1991, in ``Proceedings of the Eleventh ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems, San Diego, CA;{''} and A. Wolski and J. Veijalainen, 1990. in ``Proceedings of the International Conference on Databases, Parallel Architecture and Their Applications,{''} pp. 321-330), that strives to ensure atomicity of transactions without the usage of the 2PC protocol. We reduce the task of ensuring serializability in MDBSs in the presence of failures to solving three indepentent subproblems. solutions to which together constitute a complete strategy for failure-resilient transaction management in MDBS environments. We develop mechanisms with which each of the three subproblems can be solved without requiring any changes be made to the preexisting software of the local DBMSs and without compromising their autonomy. (C) 2001 Academic Press.