Traditional locking mechanism is fit for the concurrency controlling and data consistency maintenance undercentralized architecture, but its response is slow, so it can not be used as concurrency controlling strategy ...Traditional locking mechanism is fit for the concurrency controlling and data consistency maintenance undercentralized architecture, but its response is slow, so it can not be used as concurrency controlling strategy for real-time distributed cooperative editing system. Moreover, operation transformation and data consistency maintenancetechnology are able to assure of quick response and unconstraint, but can't solve the context-specific inconsistencyproblems. Enlightened by the idea of operation transformation and optimistic locking mechanism, we bring forwardthe concurrency control algorithm of optimistic locking based on relative position. In this algorithm, the start positionof locking region and the position of operation are relative, and they are not transformed into absolute position untiloperations are sent to cooperative sites. Furthermore, any coeditor can edit in advance before his/her locking is con-firmed. If his/her locking is successful, the previous operations go into effect, or else undo these previous operations.We have analyzed the actual applications and can find that the possibility of undoing the previous editing operationsbecause of locking conflict is very little. So this concurrency controlling algorithm has virtues of quick response, nicedata consistency maintenance etc.展开更多
在移动分布式数据库系统中采用三层结构,提出了DMVOCC-DA-2PLV(Distributed Multiversion Opti mis-tic Concurrency Control-Dynamic Adjust ment of Serialization Order-Two-Phase Local Validation)协议处理移动分布式实时事务。移...在移动分布式数据库系统中采用三层结构,提出了DMVOCC-DA-2PLV(Distributed Multiversion Opti mis-tic Concurrency Control-Dynamic Adjust ment of Serialization Order-Two-Phase Local Validation)协议处理移动分布式实时事务。移动实时事务处理分两阶段进行。第一阶段在移动主机(MHs)上处理,并进行局部部分有效性检查性确认,使用向后有效性确认机制,与在服务器提交事务进行有效性确认。及早地检测数据冲突,节省了处理和通信资源。第二阶段在服务器处理,通过局部部分有效性确认的事务,提交到服务器进行局部最终有效性确认。协议消除了移动只读事务和移动更新事务的冲突,使用多版本动态调整串行次序技术,避免了不必要的事务重启动。如果移动只读事务所有读数据项通过局部部分向后有效性确认,则可提交,大大降低了移动只读事务的响应时间。在全局有效性确认中对分布更新事务进行检查,以保证分布串行性。通过模拟仿真,对DMVOCC-DA-2PV协议进行了性能测试,并与DTO-2PC和DHP-2PL进行了比较。实验结果表明DMVOCC-DA-2PV并发控制协议要优于其它协议。展开更多
文摘Traditional locking mechanism is fit for the concurrency controlling and data consistency maintenance undercentralized architecture, but its response is slow, so it can not be used as concurrency controlling strategy for real-time distributed cooperative editing system. Moreover, operation transformation and data consistency maintenancetechnology are able to assure of quick response and unconstraint, but can't solve the context-specific inconsistencyproblems. Enlightened by the idea of operation transformation and optimistic locking mechanism, we bring forwardthe concurrency control algorithm of optimistic locking based on relative position. In this algorithm, the start positionof locking region and the position of operation are relative, and they are not transformed into absolute position untiloperations are sent to cooperative sites. Furthermore, any coeditor can edit in advance before his/her locking is con-firmed. If his/her locking is successful, the previous operations go into effect, or else undo these previous operations.We have analyzed the actual applications and can find that the possibility of undoing the previous editing operationsbecause of locking conflict is very little. So this concurrency controlling algorithm has virtues of quick response, nicedata consistency maintenance etc.
文摘在移动分布式数据库系统中采用三层结构,提出了DMVOCC-DA-2PLV(Distributed Multiversion Opti mis-tic Concurrency Control-Dynamic Adjust ment of Serialization Order-Two-Phase Local Validation)协议处理移动分布式实时事务。移动实时事务处理分两阶段进行。第一阶段在移动主机(MHs)上处理,并进行局部部分有效性检查性确认,使用向后有效性确认机制,与在服务器提交事务进行有效性确认。及早地检测数据冲突,节省了处理和通信资源。第二阶段在服务器处理,通过局部部分有效性确认的事务,提交到服务器进行局部最终有效性确认。协议消除了移动只读事务和移动更新事务的冲突,使用多版本动态调整串行次序技术,避免了不必要的事务重启动。如果移动只读事务所有读数据项通过局部部分向后有效性确认,则可提交,大大降低了移动只读事务的响应时间。在全局有效性确认中对分布更新事务进行检查,以保证分布串行性。通过模拟仿真,对DMVOCC-DA-2PV协议进行了性能测试,并与DTO-2PC和DHP-2PL进行了比较。实验结果表明DMVOCC-DA-2PV并发控制协议要优于其它协议。
