【作者】 胡文涛；

【导师】 郝忠孝；

【作者基本信息】 哈尔滨理工大学 ， 计算机应用技术， 2003， 硕士

【摘要】 近几年来，面向对象数据库(OODBS)被许多高级应用程序所采用。OODBS是类和这些类的实例的集合。在OODBS中，类和实例都被称为对象。数据库系统的一个重要特点就是能对共享数据进行操作，也就是说，数据库系统(包括OODBS)，允许多个用户同时访问共享数据。并发控制能够管理数据库的并行访问，这样它便能够保持数据库的一致性。由于OODBS的复杂性，OODBS的并发控制比传统数据库的要复杂。并发控制中的复杂性不应该降低OODBS的性能，即是，OODBS的并发控制在满足数据库一致性要求的时候，要保持性能。为了有良好的性能，一个并发控制应该提高方法间的并发度，以便更多的事务能并行运行，并且同时降低加锁开销。为了解决面向对象数据库中并发控制机制的并发度与加锁开销的关系问题，通过引入直接访问向量、运行间信息和语义可交换性，提出一个将语义可交换性与前两者结合起来的方案，提高了面向对象数据库的实例访问方法间的并发度，并且减少了加锁开销。能更早地满足请求方法的锁请求。引入嵌套事务模型，给出一个其和嵌套方法调用结合的加锁方案，并试着给出一个集成单个类上的访问方法和类层次的锁定的总的加锁机制。更多还原

【Abstract】 In the recent years, object-oriented databases(OODBs) are used in many advanced applications. OODBs are collections of classes and instances of these classes. In OODBs, both classes and instances are referred to as objects. One of the important characteristics of database systems is manipulation of shared data. That is, database systems, including OODBs, allow shared data to be accessed by multiple users at the same time. A concurrency control involves synchronization of accesses to the database so that the consistency of the database is maintained. Due to the complexity in OODBs, concurrency controls in OODBs are more complicated than those in conventional databases. The complexity in concurrency controls should not degrade the performance of OODBs. That is, concurrency controls in OODBs must keep performance while meeting the database consistency requirements. In order to have good performance, a concurrency control is designed to increase the concurrency among methods so that more transactions can run in parallel,and besides,it is to reduce the locking overhead.To solve the problem of relation of concurrency and locking overhead, by introducing direct access vector, run-time information and semantics commutativity, we give a scheme of combining semantics commutativity and the two fornamed. The scheme in the article improves the concurrency between instance access methods in object-oriented databases, and reduces the locking overhead. The lock demanders can obtain locks earlier. The model of nested transactions is introduced, which is combined with nested methods invocation in a locking scheme, and we try to give a total locking mechanism integrating the locking of the access methods on single class and class hierarchy.更多还原