Concurrency control and recovery in multidatabase systems

Abstract

There already exist many database systems which have been built and administered independently. As database applications demand increased cooperation of such independent database systems, it becomes necessary to integrate pre-existing database systems. A natural integration methods is a "bottom-up" fashion, which integrates the database systems in such a way that autonomy and heterogeneity of participant database systems are preserved. This integration results in a multidatabase system. A multidatabase system allows users uniform access to more than one database within a transaction without modifying already existing database systems. There have been a lot of research efforts on supporting distributed transactions across homogeneous multiple database systems. Distributed transaction management consists of two parts; (1) global concurrency control to preserve the traditional serializability property of transactions and (2) atomic commitment and recovery protocols to preserve atomicity property of transactions in the presence of failures. The transaction management algorithms developed in homogeneous distributed database systems are basically subject to the complete knowledge of participant database systems such as lock table, wait-for graph, transaction log. In a multidatabase system, however, it is not possible to make such information of a preexisting database system visible to others; it requires modifications to the database system. This observation leads to an important technical challenge; how to support distributed transactions in a multidatabase system while preserving autonomy and heterogeneity of pre-existing database systems. In this thesis, we first develop a locking protocol called multidatabase two-phase locking to provide the traditional serializability property for multidatabase transactions. The locking protocol is an extension of the traditional two-phase locking protocol. We also introduce a technique based on the use of a potential-wait-for...