基于Petri网合成与化简的分布式数据库系统并发控制的死锁检测

利用模块化设计的思想，首先为分布式数据库系统中各事务的每一种操作(读锁、写锁、解锁)构造一个基本的加权Petri网模型，并给出了加权Petri网共享合成的概念、然后利用共享合成技术，动态地构造各站点的加权Petri网模型，以适应系统的动态变化．此外，本文利用Petri网的化简技术，极大地简化了各站点的Petri网模型，之后利用同步合成技术构造出整个系统的Petri网模型，较好地解决了Petri网的可达性分析中可能出现的状态“爆炸”问题．最后给出了判断整个系统是否出现死锁的充分必要条件．

Deadlock Detection of Concurrency Control in Distributed Database Based on Composition and Reduction of Petri Net

First, a weighted Petri net model for every operation ( share locking, exclusive locking and unlocking) of a transaction in distributed database system was constructed using modular technique in this paper. The definition of sharing synthesis of weighted Petri nets is given in this paper. Second, the paper composes weighted Petri net models for every site using sharing synthesis. It is convenient for dynamically constructing Petri net models in order to fit to dynamic change of system state. Moreover, the paper largely reduces the weighted Petri net model for every site with reduction technique. The Petri net model for overall system is constructed using synchronizing synthesis. It solves the state explosion problem in reachability analysis of Petri nets. Last, a sufficient and necessary condition for judging whether the system is deadlock is given in the paper.