The Concurrency Control Technique Of Embedded Real-time Database System

Embedded real-time database system is one of real-time database systems that can run independently on embedded devices, It has the characters of not only the embedded system but also the real-time database system. Compared with plain real-time transaction, the real-time transaction of the embedded real-time database system must have the abilities of automatically running without human interrupt, Therefore, function alternative characteristic and compensability should be adopted into the real-time transaction model. The former makes transaction execution have many routes so as to improve the suitability of real-time transaction, thereby advancing successful-ratio of real-time transaction. And the latter can alleviate or eliminate the influence to external environment caused by defeated hard real-time transactions, improving reliability of the system. The function alternative characteristic and compensability are both two important characteristics of embedded real-time database system, and bring new challenge to the real-time transaction processing techniques.This paper mainly studies on the problems of concurrency control that are suited for embedded real-time database system based on alternative/compensation. Firstly, describes the real-time transaction model, and then discusses the new characters of concurrency control for real-time transaction which has alternative and compensation, At last, points out the main task of this paper which is to carry on researching the problem of concurrency control at the base of the conflict-free concurrency control, and to resolve the problem of concurrency control under the condition that conflict-free alternative dose not exist.According to the real-time transaction model based on alternative/compensation, this paper puts forward a new concurrency control protocol AC-Based CCP for real-time transaction. AC-Based CCP divides the concurrency control of real-time transaction based on alternative/compensation into five steps, which are analyzing the operating object, analyzing the compatibility, selecting alternative, processing the conflict and processing the compensation. And the main research object of AC-Based CCP is the conflict problem between hard real-time transactions. So a suit of new method to process the conflict is proposed in AC-Based CCP, with the purpose of reducing the probability of aborting the transaction by selecting another alternative to run, and the new method enhances the successful-ratio of the real-time transaction. AC-Based CCP also makes full use of the compensability of the real-time transaction. If...