Research On Concurrency Conctrol In Engineering Database System Supporting Cooperative Design

With the rapid development of Internet, the cooperative design system has extended from local-area network to wide-area network. Being a very important part in transaction management of database, the quality of concurrency control is one of the key criterions in evaluating the performance of a database system. This paper focuses on studying concurrency control mechanism of transaction management in distributed engineering database that supports open, cooperative design. The achievement is as follows:(1) An architecture of four-layer distributed engineering database fit for that environment is presented. The four layers are user interface layer, Web service layer, application service layer and database service layer. The function of each layer is as follows: user interface layer supplies users with friendly interfaces; Web service layer converts the user's request to application service layer by SOAP contract; application service layer deal with the user's request and then sends the results to them; database service layer stores data of cooperative design.(2) Based on the analysis of the features of cooperative design transaction in open environment and the disadvantages of the present distributed concurrency control protocol, a concurrency control protocol for cooperative design transaction in open environment is proposed. It is a multiversion two-phase lock protocol based on ordered sharing multi-granularity locks and its correctness is also tested. Under the new protocol, read-only transaction and update transaction is distinguished. The former abides the multiversion timestamp ordering protocol, while that of the latter follows the multi-granularity locking mechanism based on ordered sharing locks. Under the new protocol, the conflict between read-only transaction and update transaction can be resolved , the flexibility of transaction execution can be enhanced. That is, the new protocol is fit for the engineering database that supports cooperative design.(3) What's more, the executable algorithm of the multiversion two-phase lock protocol based on ordered sharing multi-granularity locks is also given. Based on the architecture of four-layer distributed engineering database in open environment that supports cooperative design, an experiment environment is constructed. Under such a environment, the experiment of the multiversion two-phase lock protocol based on ordered sharing multi-granularity locks is carried out and the performance of the new protocol is analyzed as well. That is, the new protocol is fit for that open environment.