A policy that reduces communication overheads by commit- ting together all transactions completed within an interval of time is examined. A model of the system involving two queues served alterna- tively with preemptions is analysed in the steady-state under Markovian assumptions. An exact and easily implementable solution is derived and is used in order to determine performance measures such as average oc- cupancy or average latency. The optimal length of the operative interval is evaluated numerically. A non-preemptive policy is simulated and is shown to be considerably less efficient than the preemptive one analysed here. A generalization to non-Markovian operative intervals is outlined.