【作者】 丁力；

【导师】 刘云生；

【作者基本信息】 华中科技大学 ， 计算机软件与理论， 2006， 硕士

【摘要】 运行在嵌入式环境下的实时数据库的事务处理和传统数据库差别很大。传统数据库中的事务处理不考虑数据和事务的定时限制,处理的是永久的数据,追求平均性能和系统的吞吐率,而主动实时嵌入式数据库根据时间紧迫度的不同,事务执行有优先级顺序,要保证尽量多的事务在截止期前完成。ARTs-EDB是自行研发、拥有自主知识产权的嵌入式主动实时数据库。ARTs-EDB设计的多线索模块化的进程结构和事务执行模型适应嵌入式微内核的结构,它具有灵活、快速和移植性好的特点,是整个系统构建的基础。一般平坦的事务模型已经不适合ARTs-EDB的需求,建立了嵌套的实时事务模型。ARTs-EDB的每个事务都有一个事务控制块,记录着事务的ID、所占资源和事务状态信息,在整个事务执行过程中事务控制块一直存在。为了满足主动实时事务及时有效的执行,首先事务的优先级分配需要结合事务的截止期,事务调度要按照事务的优先级,其次事务需要在执行前进行预处理操作,以便事务真正执行时提前把所需数据都存放在内存缓冲区,最后由于事务存在依赖性,事务在开始、提交或夭折时,必须考虑到与主动机制的联系。ARTs-EDB建立了有效的事务执行模型。通过事务的接纳、放行的管理,控制了在内存中事务的数量,使事务执行所需的数据装入内存。通过事务调度,执行管理确保了高优先级的事务先执行。更多还原

【Abstract】 Runing under embedded environment, real-time database has great difference on transaction processing from traditional database. Traditional database doesn’t consider the time limitation of data and transaction, whose object is average performance and system throughout, while active real-time embedded database tries its best to assure more transactions committed before their deadlines on the basis of their priorities.ARTs-EDB is an embedded active real-time database system researched and developed independently.Having the characters of flexibility, briskness and good migration, the multi-thread and modularized process structure and transaction execution model meets embedded micro-kernel construction, which is the foundation of the whole system construction.The normal flat transaction model is not satisfied for the need of ARTs-EDB.So a nested transaction model is builded.Every transaction of ARTs-EDB have a transaction process block,which addresses the ID,needed resource and status of it and exist during its lifecycle.For satisfied the effective and time constrains’ececution of transactions,first of all, transaction priority assignment should take into account transaction’deadline, scheduling transaction should take into account transaction priority.Second ,in order to load all needed data into memory before transactions’exectution,transactions need pre-analysis.Last,because the depend of transactions,when a begin,commit or abort operation of transactions occur,should take active mechanism into count.ARTs-EDB build a effective execution model of transaction.First, transaction admiting and releasing makes sure the max numbers of transactions in memory,and the data they need also in memory.Second,the highest priority transaction executes first by transaction scheduling.更多还原