Integrating Snapshot Isolation Into Transactional Federations

This paper reconsiders the problem of transactional federations, more specifically the concurrency control issue, with particular consideration of component systems that provide only snapshot isolation, which is the default setting in Oracle and widely used in practice. The paper derives criteria and practical protocols for guaranteeing global serializability at the federation level. The paper generalizes the well-known ticket method and develops novel federation-level graph testing methods to incorporate sub-serializability component systems like Oracle. These contributions are embedded in a practical project that built a CORBAbased federated database architecture suitable for modern Internetor Intranet-based applications such as electronic commerce. This prototype system, which includes a federated transaction manager coined TraFIC (Transactional Federation of Information Systems Based on CORBA), has been fully implemented with support for Oracle and O2 as component systems and using Orbix as federation middleware. The paper presents performance measurements that demonstrate the viability of the developed concurrency control methods.