Transaction commit in a realistic fault model

We study the transaction commit pro.blem under realistic timing assumptions. We identify an almost asynchronous model, which we claim is more realistic than some (synchronous) models that have been studied previously. In this model we give a randomized transaction commit protocol based on Ben-Or's randomized asynchronous Byzantine agreement protocol. The expected number of asynchronous rounds until our protocol terminates is a small constant, and the number of failstop faults tolerated is optimal. It is known that no deterministic protocol is possible in this model. We motivate our definition of asyn-chronous rounds by showing that no protocol in this model can terminate in a bounded expected number of clock ticks, even if processors are synchronous. Defining asynchronous rounds allows us to make the performance guarantee that after a sufficient number of useful messages have been delivered our protocol will terminate.