(A) global transaction management scheme in multidatabase systems

Abstract

A multidatabase system (MDBS) is an integration of pre-existing local database systems (LDBSs), which supports global applications that access more than one LDBS. The main goal of multidatabase transaction management is to guarantee multidatabase consistency, even in the presence of failures, while maintaining local autonomy. It has been shown that correct executions of multidatabase transactions cannot be achieved in the failure-prone environment without certain trade-offs on local autonomy and/or semantic-freeness of transactions. Therefore, many works on multidatabase transaction management have been made in the past with some assumptions that are, in general, difficult to justify in real world multidatabase environments. In this thesis, our goal is to develop failure-resilient multidatabase transaction management techniques that are independent of semantics of the transaction applications as well as the database integrity constraints (implicit or explicit), so that it can be widely applicable. Our technique can be used not only for a centralized but also for a decentralized MDBS environment, to prevent the blocking of the execution of global transactions at all sites due to the crash of a single site. Also, the proposed methods should be applicable irrespective of types of global transactions depending on transactional interfaces that are exported by local database systems to the multidatabase system. Since user organizations in an MDBS are autonomous and have pre-established LDBS, it is essential that MDBS construction must not require major modifications to existing DBMS software while providing users with a consistent and reliable database. We first clarify the global transaction management issues and review the previous works. Then, we define a decentralized MDBS model and propose some transaction processing methods for our multidatabase system. As a global concurrency control method, the multidatabase strict two-phase locking (M-S2PL) protocol is pre...