移动复制数据库系统冲突检测及消解策略*

丁治明1   王珊2，1   孟小峰2

1 (中国科学院计算技术研究所 北京 100080)

2 (中国人民大学数据与知识工程研究所 北京 100872)

 

摘 要   复制技术是提高移动数据库系统性能的一项关键技术。本文提出了一种新的移动复制数据库系统模型─事务级结果集传递（TLRSP）移动复制模型，重点分析了该模型中的冲突检测及消解策略，并给出了具体的实现算法；TLRSP移动复制模型允许移动用户在系统断连时存取数据库的本地副本并提交事务，重新连接时进行冲突的检测及消解，同时进行事务结果集的合并，最后通过增量刷新的方式进行同步处理，使得系统收敛于一致性的状态。此外，通过引入简化的事务日志、数据版本号及权限控制等概念，TLRSP模型有效地降低了移动数据库系统的资源消耗，保证了数据库的一致性，从而为移动数据库系统复制技术提供了一个可行的解决方案。

关键词   移动计算，数据库，事务处理，复制，冲突处理.

CONFLICT DETECTION AND RESOLUSION STRATEGY IN REPLICATED MOBILE DATABASE SYSTEMS

Ding Zhiming1       Wang Shan2，1        Meng Xiaofeng2

1(Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100080)

2(Institute of Data and Knowledge Engineering, Renmin University of China, Beijing 100872)

Abstract       Replication is one of the key technologies in promoting the performance of mobile database systems. A lot of research has been focused on mobile database replication recently, and many models and algorithms have been proposed. However, most of the work does not focus on the conflict reconciliation problem. Some approaches that do focus on the conflict resolution require specialized knowledge of the system for all transactions and special concurrency control models, which limits their adaptability. Besides, some proposed methods do not ensure transaction serializability, which can cause serious consistency problems in many circumstances. In order to solve these problems, a new mobile database replication scheme, Transaction-Level Result-Set Propagation (TLRSP) model, is put forward in this paper. The conflict detection and resolution strategy of TLRSP model is discussed in detail, and the implementation algorithm is proposed. In TLRSP model, mobile users are allowed to access local replicas of the database and locally commit mobile transactions when the system is disconnected. The locally committed transactions are sent to the fixed database server for conflict reconciliation and result-set incorporation when the system is reconnected. In order to ensure database consistency, transactions locally committed at mobile hosts need to be validated at the database server before they can be globally committed. Mobile transactions that have executed conflicting operations will be aborted, and only those mobile transactions that do not violate the consistency of the database server can be globally committed. TLRSP model uses an incremental refresh method, and only recently updated data need to be transmitted during the synchronization process. Besides, by utilizing a simplified log structure and by introducing version number and access control into the system, TLRSP model reduces the resource consumption and communication costs. To sum up, through an efficient conflict reconciliation and result-set propagation strategy, TLRSP model provides a flexible and effective solution to the replication problem of mobile database systems.

Keywords: Mobile Computing, Database, Transaction Processing, Replication, Conflict Reconciliation.

 


* 本课题得到国家863高科技基金(863-306-ZD12-12-1)及国家自然科学基金(60073014)的资助。丁治明 (1966年生)，高级工程师、博士研究生，主要研究方向为数据库与知识库系统、移动计算；孟小峰 (1964年生)，教授、博士，主要研究方向为数据库与知识库系统、移动计算；王珊 (1944年生)，教授、博士生导师，主要研究方向为数据库与知识库系统、移动数据库。