Increasing the Resilience of Distributed and Replicated Database Systems

This paper presents a new atomic commitment protocol enhanced three phase commit E PC that always allows a quorum in the system to make progress Previously suggested quorum based protocols e g the quorum based three phase commit PC Ske allow a quorum to make progress in case of one failure If failures cascade however and the quorum in the system is lost i e at a given time no quorum component exists a quorum can later become connected and still remain blocked With our protocol a connected quorum never blocks E PC is based on the quorum based PC Ske and it does not require more time or communication than PC We describe how this protocol can be exploited in a replicated database setting making the database always available to a majority of the sites