Multi-Criteria: Degrees of Recoverability in Distributed Databases

This paper concerns distributed databases and transactions with a distinction between global and local correctness criteria. The global requirements per system are weaker than the local requirements per site. The paper investigates an application which suits such a two-level division. The main motivation for our investigation is based on the fact that the commonly used correctness criteria for concurrency control and recovery, serializability and total recoverability, are very strict criteria. The use of more relaxed criteria (allowing more true parallel behaviour and more true partial behaviour) is therefore very appealing — as long as this can be achieved without compromising safety or applicability. The main paradigm in our approach is based on the observation that relatively little knowledge about the databases and transactions can lead to major gains in system throughput. This allows specific systems to have more tailor-made correctness criteria.