一种复制数据库恢复协议研究

数据复制是提高数据库系统性能和可用性的重要技术。近年来出现的基于组通信技术的数据库复制协议较之传统的数据库复制协议因其实现简单灵活、性能较优，在构建实用复制数据库系统时得到广泛应用，维持各节点副本一致性是数据复制技术研究的核心问题。本文讨论了当故障节点恢复后重新加入系统或增加新节点后如何恢复、维护系统节节点副本间的一致性的问题。本文提出了一个针对分布复制数据库系统的恢复协议，该协议结合基于组通信技术的复制协议，可在不影响系统正常事务处理的情况下，实现故障恢复后节点或全新节点重新加入系统时的系统正确恢复，并给出了理论证明。同时还证明，该恢复协议对于分布在不可靠网络上的复制数据库的恢复问题同样适用。

On a Recovery Protocol for Replicated Databases

Database replication is a well-known technique for increasing performance(response time,throughput,etc.)and availability in distributed databases.Over the past few years,a database replication protocol based on group communication has been widely used in constructing practical replicated databases for its advantages in easier and more flexible implementation with good performance compared to traditional replication protocols.To keep the consistency of all replicas on sites is a key problem of the research in database replication.This paper discusses the problem of how to regain the consistency of replicas after the recovery of the failed sites or adding new sites.A recovery protocol for distributed replicated databases is provided.Combined with the replication protocol based on group communication,the protocol can make the replicated system recover correctly after a site,which is completely new or has recovered from a failure,rejoining the system,while the whole system can still process transactions without being interrupted.We give a theoretical correctness proof of it,and also prove that it is suitable for the replicated databases which are distributed on an unreliable network.