Fault Tolerance in Three-Tier Applications: Focusing on the Database Tier

The paper discusses the issues involved in providing an integrated fault-tolerance solution to enterprise applications with distributed three-tier architecture. We examine end-to-end fault-tolerance requirements for interactions between the tiers and describe available solutions. We do a detailed assessment of fault-tolerance technologies available for the database tier, which poses most challenging reliability and high-availability problems. In particular, we discuss and compare the tradeoffs made in commercial database systems between different aspects of fault-tolerance.