Research And Implementation Of The Storage Mechanism Of Embedded And Mobile Database

With the development of the micro-electronics technology and the mobile communication technology,the capability of the embedded facility and the mobile facility has become increasingly powerful. So, many people hope that the embedded and mobile terminal would be a private working platform of next generation and a portable platform for mobile business. A new application mode, that is, the embedded and mobile application mode, is getting more and more attention. As like the e-business was supported strongly by the traditional disk DBMS, the new application mode must get support from the embedded and mobile DBMS (For short, we call it EMDBMS) before it will be accepted by most users. But there is little research on EMDBMS at present. Although there are a few productions that have been developed, they have not been accepted because they can not satisfy all the characteristics of the embedded and mobile computing environment. This dissertation has carried on systemic research on the storage policy of EMDBMS, and put forward one way to realize it. All of that has laid a good foundation for the full realization of EMDBMS. In order to adapt to the characteristics of the embedded and mobile computing environment, the design of the database system should obey the following policies: micro-kernel, standardization, being layered designed and deployed. In the storage tier, it should pay more attention to the rational utilization of the limited resources, and adopt the way of memory buffer to promote systematic function. In order to achieve high adaptability and be accepted rapidly by the current development communities, the storage tier, which is considered to be compatible to PC, uses relation data model. In this dissertation, the concept of working edition space (WES) is put forward which is the memory-resident data version in the database runtime, and is a high-activeness subset of the complete data edition of database. Comparatively to WES, the permanent edition space (PES) is the data edition which is stored in the external storage, and at a certain moment, it is an intact data snapshot of the database which accords with consistency. The system adopts the optimistic tactics of data recovery, weaken the treatment to PES, and pay more attention to the organization of WES. Such tactics have simplified the process of physical organization of data and memory space management greatly, and have good efficiency. Meanwhile, in order to maintain the data consistency between EMDBMS and central database server, this dissertation proposes a data synchronous mechanism which is supported in the storage tier. In order to optimize the data access performance, the MF-AVL index structure and the data elimination strategy in WES which can accurately describe the data activity are proposed. The former is a mutation of AVL tree, which can well meet the way of data organization of EMDBMS and offer high-efficient access paths. The latter can guarantee what is stored in WES is high-activeness data. It can prevent the limitless growth of the requirement for memory and be beneficial to utilize memory efficiently and promote systematic access performance.