Distributed transaction systems require an atomic commitment protocol to preserve ACID properties. A commit protocol should add as little overhead as possible to avoid hampering performance. In this paper, dynamic coordinators are introduced. In main memory primary-backup systems, the approach significantly reduces the time spent during commit processing. The performance of such protocols must be properly evaluated to give system developers the information needed to make an educated choice between them. Thus, simulation results, verified by statistical analysis, are presented. The simulation results show that the performance can be significantly boosted by using optimizations and protocols especially designed for high availability main memory systems.