【作者】 梁平；

【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， 2011， 博士

【摘要】 在嵌入式实时环境下,适合于不同应用需求的恢复策略是嵌入式实时数据库系统能够可靠、高效运行的关键。在分析嵌入式实时数据库系统的数据、事务的特征以及故障恢复需求特征的基础上,分别从嵌入式实时数据库系统基于实时日志的故障恢复策略、检验点策略、重装策略及在移动环境下应用的恢复这几个方面进行了研究,以获得嵌入式实时数据库系统的健壮性和高可用性。根据嵌入式实时数据库中数据及事务的定时要求及其在嵌入式应用环境下的特殊需求,结合ARTs-EDB,给出了以内存数据库作为底层支持的嵌入式实时数据库管理系统结构及组成。并在此基础上,给出了嵌入式实时数据库恢复系统的体系结构。对嵌入式实时数据库系统中数据和事务的特征及其一致性进行了分析,并基于此给出了嵌入式实时数据库系统恢复的特征及需求。为了在系统故障时保证嵌入式实时数据库系统中数据的时间一致性、恢复时间的可预测性、快速而及时的恢复以及恢复的低开销,讨论了基于实时日志的故障恢复策略。基于嵌入式实时数据库ARTs-EDB,设计了一种实时模糊检验点策略以减少嵌入式实时数据库系统超截止期事务的数量及故障后的快速恢复。同时,讨论了故障恢复时相应重做起点的确定策略以保证故障恢复时提交事务的持久性及减少恢复时间。为了满足嵌入式实时内存数据库中数据和事务的定时限制,减少超截止期事务数量和恢复时间,讨论了一种基于数据段优先级的分区检验点策略SPPFCS,并给出了相应故障恢复时基于数据段优先级的分区重装策略SPPRS。SPPFCS根据数据段优先级对数据库进行分区并为每个分区设置相应的检验点频率以进行分区检验点操作,降低了系统中事务超截止期比例并减少了恢复时间。分区重装策略SPPRS根据数据分区的检验点频率来分区重装数据库,减少了系统停止服务时间,并且考虑了事务对数据的请求,提高了恢复过程中系统的可用性。在移动环境下,嵌入式实时数据库系统的健壮性和高可用性也体现在系统中应用的恢复。为了增强应用的可用性,提出了一种在移动环境下支持应用恢复的基于移动代理的体系结构,并给出了基于该移动代理结构的日志管理方案。日志管理中的日志合并策略及传送通知消息策略不仅减少了恢复时间,而且在过区切换日志管理代价、日志检索代价及故障代价三个方面都获得了较好的、一致的系统性能。更多还原

【Abstract】 The recovery strategy suitable for different demands of applications is critical to the embedded real-time database systems which can be running reliably and effectively in the embedded real-time environment. To achieve the robustness and the high availability of the embedded real-time database systems, the failure recovery strategy based on real-time logs, checkpoint strategy, reload strategy and the applications recovery in mobile environment are researched on the basis of analyzing the characteristics of data and transactions of the embedded real-time database systems.According to the special needs of embedded applications and the timing constraints of data and transactions in embedded real-time databases, the architecture and the system composition of the embedded real-time database management system which use the main memory databases as the underlying support are presented. Furthermore, the architecture of the recovery system is also presented.The characteristics and the consistency of data and transactions in embedded real-time database systems are analyzed, moreover, the recovery characteristics and demands are proposed based on the analysis.In order to guarantee the time consistency, the predictability of recovery time, fast and timely recovery, as well as the low recovery overhead in system failures, the failure recovery strategy based on real-time logs is discussed.A real-time fuzzy checkpoint strategy supporting the embedded real-time database systems is designed to reduce the number of the transactions which miss their deadlines and get a rapid recovery after a failure on the basis of embedded real-time databases ARTs-EDB. Besides, the strategy to determine the redo point in failure recovery is discussed to ensure the durability of the committed transactions during failure recovery and decrease the recovery time. For the sake of meeting the data and transactions timing constraints, as well as reducing the number of transactions missing their deadlines and recovery time in the embedded real-time main memory database systems, a partition checkpoint strategy SPPFCS based on the priority of data segments is presented, and what’s more, a partition reload strategy SPPRS in failure recovery is discussed accordingly. SPPFCS partitions the database in accordance with the priority of data segments, and sets the corresponding checkpoint frequency for each partition to execute the partition checkpoint operations, which reduces the ratio of the transactions missing their deadlines and the recovery time. SPPRS reload the database in the light of partition checkpoint priority which reduces the system halt servicing time and improves the system availability during the recovery for considering the requests of the transactions to data.The robustness and the high availability of the embedded real-time database systems are also reflected in system applications recovery in mobile environment. A mobile agent-based framework for supporting applications recovery in a mobile environment is presented to improve the availability of the applications. A log management scheme on the basis of this mobile agent-based framework is also proposed. Log unification strategy and sending notification message strategy in log management are not only reduce the recovery time, but also have the better and consistent system performance on handoff log management costs, log retrieval costs and failure costs.更多还原