As the development of mobile-computing, mobile-commerce and informative electric appliance, the Embedded Database Management System(EDBMS) has appeared recently as a new data management technology. The EDBMS implements the functions of data storage, data organization and data management, which based on the mature database technology and aimed at the idiographic embedded applications.ARTs-EDB is an embedded active real-time database management system, which is supported by main-memory database system. So it can ensure no data I/O access when transactions are running. ARTs-EDB was designed to have modularized process structure with multi-thread on the top of an embedded micro-kernel. It can easily be ported to the other embedded operating systems.The traditional atomic transaction model with ACID properties can not meet the requirements of real-time and active database systems. ARTs-EDB adopts a nested transaction model admitting a transaction and its sub-transactions to share data.There are great differences between traditional database and embedded active real-time database on processing transactions. Transactions'processing in traditional databases does not regard to the timing constraints of data and transactions, and the data processed are permanent. The more we care about is the average performance and the throughput of a system. Whereas the miss deadline percentage and restart ratio are more crucial to active real-time database. ARTs-EDB assigns the transactions'priority according to their deadlines, and makes concurrency control based on the priority. This policy can ensure the active real-time transactions to be processed timely and effectively.Because the concurrency control policy ARTs-EDB adopted mainly depend on priority and conflicting transactions aborted, it may lead to high abort ratio especially those transactions who have higher priority, and to some extend affect the performance of the system. So it needs to be improved. The improved policy can ensure the transactions with high priority and control the abort ratio especially the abort account of those transactions with higher priority, and therefore improve the performance of the system. |