【作者】 陈国宁；

【导师】 李陶深； 兰红星；

【作者基本信息】 广西大学 ， 控制理论与控制工程， 2002， 硕士

【摘要】 支持协作的工程数据库系统为计算机支持的协作设计提供数据管理，使协作设计活动能有效地操作正确的和可靠的设计数据对象。事务管理是整个系统的核心部分。本论文对协作设计活动和协作设计事务模型进行了描述，并对支持协作的工程数据库事务管理系统的功能结构、并发控制机制、事务提交机制和恢复处理等方面进行了研究，同时，在样机系统中对上述研究进行实验和分析。 在深入分析协作设计的特点后，对协作设计活动的描述进行了初步探讨；并在此基础上，提出了一个支持协作设计的事务模型。该事务模型结合了部分已有事务模型的优点，采用类似于嵌套结构的事务结构，使事务的提交和夭折更灵活。同时，该模型允许子事务间可以进行交互，从而支持协作的进行。 提出了两种支持协作设计的并发控制方法：基于有序相容性封锁的多粒度封锁机制和基于有序相容性封锁的CBR封锁机制。在基于有序相容性封锁的多粒度封锁机制中我们对简单的锁模型进行了扩充，在共享锁(S／R)和排它锁(X／W)的基础上增加了几种锁，并建立了相应的锁相容性矩阵，同时给出封锁协议和实现算法。该方法对协作读和协作修改设计事务提供了支持。基于有序相容性封锁的CBR封锁机制是在考虑同一场地设计事务的延续性而提出的。该协议可提高在同一场地执行的事务对象申请的成功率，同时也具备了一定的协作支持能力。 提出了带有时限的工程设计事务两阶段提交协议，包括其原理及其对故障的处理方法。该协议一方面允许设计子事务在设计期限未到之前“先”提交，同时在本组事务满足提交条件或者说某一设计方案完成的情况下可提交而不用等待最后期限，从而给设计活动的开展提供更大的灵活性；另一方面，在设计期限到来时，如果本组的设计任务仍然不能提交，则小组协调者可强制要求未完成的子事务进行汇报，以决定是否可以最终提交，从而保证了设计任务按时完成。 提出了保存点savepoint机制。该机制采用冗余存储的方法，将设计事务各阶段的结果保存在小组服务器中，减少了失败时带来的工作损失，同时通过savepoint号(SN)关联的办法，解决了协作产生的数据相关性在恢复处理时可能带来的级联恢复问题。在此基础上，提出了基于日志与savepoint机制的恢复算法。该算法能处理协作设计过程中出现的大部分场地故障。 最后，在样机系统中，分别对基于有序相容性封锁的多粒度封锁机制和带有时限的工程设计事务两阶段提交协议进行了实验和分析。实验表明我们的想法是正确的和可行的。更多还原

【Abstract】 Engineering database system (EDBS) supporting cooperation provides the data object management for computer supported cooperative design (CSCD). Transaction management is the hardcore of the EDBS. This paper discusses several researching results on transaction management in EDBS supporting cooperation. It includes the description of cooperative activities and cooperative transaction model, the functional structure of the transaction process system in EDBS supporting cooperation, the concurrency control mechanism, the commit protocol and the recovery process. And the experiment in a prototype system based on the research above is presented as well.Given the characteristics of cooperative design environment, the description of cooperative design activities is presented. Based on the description, a cooperative transaction model is proposed. The model has a nested hierarchical structure and adopts some advantages of other transaction models, which makes it more flexible. And the model provides some interaction between two sub-transactions so that it can provide partly cooperation between design transactions.Two concurrency control methods that support cooperative design transaction are presented. In multi-granularity locking mechanism based on ordered sharing locks, we extend the simple lock mode-Shared lock(S/R Lock)/Exclusive lock(X/W Lock) by introducing several other locks. The corresponding compatible matrix is given. The locking protocol and the locking algorithms is also presented. This method can support cooperate design transaction of read and update. The other method is CBR locking mechanism based on ordered sharing locks. It is developed by considering the continuity of the serial transactions executed in a same local client. The locking protocol is presented. This method can also support some cooperation.The timeout-trigger Two-Phases Commit protocol for engineering design transaction is proposed. The principles and the fault process of the protocol are presented. On one hand, the protocol allows ’early’ commit in participant transactions and ’early’ commit of-n-coordinator transaction before timeout, if the finishing condition is held. On the other hand, if the coordinator can’t commit after timeout comes, the coordinator can force the uncommitted participants to vote, and make final decision according to the votes.A mechanism named savepoint is also developed. The mechanism adopts redundant storage. It stores the partly design result to server during the design according to the command of users, so that it can diminish the lost of fault. It can support some cooperation through broadcast. And it can solve cascading recovery by using savepoint number (SN). A recovery algorithm based on log and savepoint mechanism is also developed. The algorithm can resolve most site fault in cooperative design and provide some selected rollback.In the end, the experiment of the multi-granularity locking mechanism based on ordered sharing locks and timeout-trigger two-phases commit protocol for engineering design transaction is executed in a prototype system. The analysis of the results are also given. The experiment proves that our thoughts are correct and feasible.更多还原