Comparing the Atomic Commitment and Consensus Problems

Abstract

Reaching agreement in a distributed system is a fundamental issue of both theoretical and practical importance. Consensus and non-blocking atomic commitment are two wellknown versions of this paradigm. The Consensus problem considers a fixed collection of processors each of which has an initial value drawn from some domain V , and processors must eventually decide on the same value¹; moreover, the decision value must be the initial value of some processor. The non-blocking atomic commitment (NB-AC) problem arises in distributed database systems to ensure the consistent termination of transactions. Each process that participates in the processing of a database transaction arrives at an initial opinion (vote) about whether to commit the transaction or abort it. Processes must eventually reach a common decision (commit or abort). The decision to commit may be reached only if all processes initially vote to commit. In this case, “commit” must be reached if there is no failure.