本文選題：嵌入式數(shù)據(jù)庫　切入點：恢復　出處：《華中科技大學》2012年碩士論文　論文類型：學位論文

【摘要】：隨著嵌入式技術的不斷發(fā)展，嵌入式數(shù)據(jù)庫應用得越來越廣泛。嵌入式環(huán)境有許多特點和限制，如移動性、網(wǎng)絡不穩(wěn)定性以及電源能力等，對嵌入式數(shù)據(jù)庫可靠性和性能提出了更高的要求和挑戰(zhàn)，一個強健的恢復子系統(tǒng)是嵌入式數(shù)據(jù)庫必不可少的組成部分。通過系統(tǒng)深入地研究數(shù)據(jù)庫恢復技術，對達夢(DM)嵌入式數(shù)據(jù)庫恢復子系統(tǒng)進行了改進，以提升系統(tǒng)可靠性和可用性。 為適應嵌入式環(huán)境，使系統(tǒng)設計遵循簡約性和微內(nèi)核特性，對數(shù)據(jù)庫回滾段進行了設計與改進，將回滾段集成到數(shù)據(jù)文件中，進行系統(tǒng)恢復時僅搜索預留回滾段，節(jié)省了恢復時間；同時將日志文件設計成單日志形式，并采用事務一致性檢查點縮短恢復時需要掃描的日志量。 在系統(tǒng)故障恢復時，為避免對所有Redo日志進行重做，設計并實現(xiàn)了選擇性重做方案。對于那些已經(jīng)寫入到數(shù)據(jù)庫文件中的記錄，根據(jù)頁面的日志序列號(LogSequence Number, LSN)和日志記錄的LSN進行判斷后再決定是否進行重做，而不是盲目地重做，分析并給出了使用該方法的前提條件。該方法節(jié)省了系統(tǒng)緩沖區(qū)資源，減少磁盤I/O，體現(xiàn)了嵌入式數(shù)據(jù)庫微內(nèi)核的要求。 為充分利用操作系統(tǒng)多道程序設計思想以及達夢嵌入式數(shù)據(jù)庫特殊的事務模型，系統(tǒng)恢復時采用多線程方式重做日志加速恢復。使用一個日志分發(fā)線程、多個重做線程的模型，線程間同步協(xié)作完成重現(xiàn)歷史操作，達到快速重建系統(tǒng)崩潰時系統(tǒng)狀態(tài)的目的。 經(jīng)過實驗測試表明，改進后的恢復子系統(tǒng)能正確處理系統(tǒng)遇到的事務故障、系統(tǒng)故障和介質(zhì)故障，且能縮短系統(tǒng)故障恢復使用的時間。
[Abstract]:With the continuous development of embedded technology, embedded database is more and more widely used. Embedded environment has many characteristics and limitations, such as mobility, network instability and power supply ability, etc. This paper puts forward higher requirements and challenges to the reliability and performance of embedded database. A robust recovery subsystem is an essential part of embedded database. In order to improve the reliability and availability of the Darmenton (DMN) embedded database recovery subsystem, the system is improved. In order to adapt to the embedded environment and make the system design follow the characteristics of minimization and microkernel, the database rollback segment is designed and improved. The rollback segment is integrated into the data file, and only the reserved rollback segment is searched for system recovery. The recovery time is saved and the log file is designed as a single log form and the amount of logs that need to be scanned is shortened by using transaction consistency checkpoint. In order to avoid redoing all Redo logs during system recovery, a selective redo scheme is designed and implemented. According to the log sequence number of the page, LogSequence number (LSNs) and the LSN of the log record, we can decide whether to redo it or not instead of blindly redoing it. The precondition of using this method is analyzed and given. This method saves the system buffer resource. Reducing disk I / O reflects the requirement of embedded database microkernel. In order to make full use of the multiprogramming idea of operating system and the special transaction model of Dameng embedded database, the multithread redo log is used to speed up the recovery of the system, and a log distributing thread is used. In the model of multiple redo threads, the synchronization and cooperation between threads complete the reproducing history operation, so as to quickly reconstruct the system state when the system crashes. The experimental results show that the improved recovery subsystem can correctly deal with the transaction faults, system failures and medium failures encountered by the system, and can shorten the time of system fault recovery.
【學位授予單位】：華中科技大學
【學位級別】：碩士
【學位授予年份】：2012
【分類號】：TP368.1;TP311.52

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