Transaction Management in a Heterogeneous Database Environment

9221301 Silberschatz异构数据库环境中的事务管理这是一个持续三年的奖项的第一年。多数据库系统（mdb）由许多运行不同商业数据库管理系统（dbms）的站点组成。mdb的目标是集成dbms，允许应用程序访问来自各个dbms的数据，而不需要对其进行修改。多数据库系统中的自治用户组织通常在DBMS上投入了大量资金，并且可能不愿意修改或失去对DBMS的控制，这是正确的。因此，必须开发允许高度本地自治的多数据库事务处理方法，同时以一致和可靠的方式支持用户的数据。本研究探讨了如何管理和保证驻留在异构dbms中的数据的一致性，同时遵守参与dbms的自治需求。本研究开发的MDBS事务管理方案具有以下特点：(1)适应MDBS环境，现有的基于保持事务原子性和序列化性的数据库一致性技术；(2)利用替代的正确性标准来放松序列化性和原子性要求。为可序列化性和宽松可序列化性模型开发的试验系统用于进行性能评估，以确定所开发的方案允许高度的并发性。研究结果将为开发完整的多数据库管理系统提供必要的基本事务管理机制。＊＊＊

9221301 Silberschatz Transaction Management in a Heterogeneous Database Environment This is the first year of a three-year continuing award. A multidatabase system (MDBS) consists of a number of sites which run distinct commercial database management systems (DBMSs). The goal of an MDBS is to integrate the DBMSs, allowing applications to access data from, without requiring modifications to, the individual DBMSs. The autonomous user organizations in a multidatabase system generally have invested substantial capital in the DBMS and may, rightly, be unwilling to modify or lose control over their DBMSs. Therefore, it is imperative to develop multidatabase transaction processing methods that allow a high degree of local autonomy, but support users' data in a consistent and reliable manner. This research investigates how to manage and guarantee consistency of data residing in heterogeneous DBMSs, while adhering to the autonomy requirements of the participant DBMSs. The MDBS transaction management schemes developed in this research have the following characteristics: (1) adapt to MDBS environments, existing techniques for ensuring database consistency based on preserving transaction atomicity and serializability; (2) utilize alternate correctness criteria that relax the serializability and atomicity requirements. Pilot systems developed for both the serializability and the relaxed serializability models are used to conduct performance evaluation to ascertain that the developed schemes permit a high degree of concurrency. The results of the research will provide the basic transaction management mechanisms necessary for the development of a complete multidatabase management system. ***