Research And Application Of The Distributed Memory Database Redundancy Allocation

Data redundancy is a key feature of the distributed database. Although the redundancy allocation of distributed memory database is similar to the traditional distributed database allocation problem, it is distinct in other features. This thesis studies general redundancy allocation methods, and then implements a heuristic allocation strategy that the copies are restricted. Basic characteristics of the memory database are considered so that the strategy is more suitable for the distributed memory database.The strategy’s main steps are similar to the traditional heuristic allocation algorithm. It is made of two main sections:initially assignment and dynamically adjustment. But it sets up two limit values for the copies which is different from other methods. One of the limit values is the lower bound and the other is the upper bound. The lower bound is used to guarantee the fewest copies of the fragments and the upper one is used to limit the most copies. These two values make sure the system stable and reduce the store spaces for the copies. In some scenarios, the upper bound can speed up the allocation calculation. Due to the limitation of the memory size, most times it can’t initial all data fragments at the same time as the traditional allocation methods. So the strategy sorting the fragments bases on the statistics information during the initialization, and then allocates them by the orders.The redundancy allocation algorithms almost built on the certain basic information and statistics information. There are many parameters which will impact the fragment allocation. During the allocation experiments, often need to adjust the model size and set the values of the parameters, which greatly increasing the workload for the model solving. A redundancy allocation parameters management system is designed and implemented in this thesis. The system is based on B/S architecture and J2EE frameworks. Users can maintain the various parameters to affect the allocation results and also can select different algorithms for the data allocation experiments.The parameter management system provides data supporting and strategy choosing for the decision of distributed memory database fragments redundancy allocation. The experiment result shows the limit copies method is suitable for distributed memory database redundancy allocation and it can control the copies of every fragment and speed up the calculation.