Abstract: Long-distance education based on Data Grid provides geographically distributed education resources.However，ensuring efficient and fast access to such huge and widely distributed resources is hindered by the high latencies of the Internet.Replication is adopted to address these problems.Aiming at replica creation，a model to decide replica creation opportune moment is introduced，which is based on queuing theory.Through statistical record of the arrival rate of uses，service period，and replicas already created，calculating length of queue，waiting duration time，busy period，service strength and so on，a reasonable creation opportune moment of replica can be obtained.

摘要： 基于数据网格的远程教育提供了地理分布的大量共享教育资源，然而互联网的高访问延迟降低了资源访问的效率。副本创建是一种提高访问效率的有效方法。提出了一种基于排队论的副本创建时机决策模型，通过统计记录系统中用户请求到达的时间、任务服务的时间、副本已创建数等，计算排队系统队长、逗留时间、等候时间、忙期、服务强度及系统的瞬时状态等，由此得出一个比较合理的副本创建时机。