| The unpredictable software and hardware failures can influence the implementation of transactions or even undermine the database in database management system, and reduce its reliability and availability. Backup and recovery subsystem is to solve these problems. Subject to the"large-scale development and application of generic database management system DM V5.6"as background, we study the database backup and recovery technology and improve backup and recovery subsystem to improve the reliability and availability.Based on the existing DM database backup and recovery subsystem we work on the four main areas, including backup and log multi-file, asynchronous checkpoint, time-based recovery and parallel recovery. Backup multi-file is that a backup operation can produce a number of backup files if need, making the transfer of backup files easier. Log multi-file uses two or more log files circularly to avoid the problem of ever-increasing individual log file.When setting asynchronous checkpoint, we S lock a dirty page, flush the dirty page, then release the S lock after the flushing finished. The transactions can also update pages in the interval of asynchronous checkpoint.Time-based recovery creates a time type log and inserts a time type log in the end of a physical transaction to mark the end time of the physical transaction. When using time-based recovery, we only need to redo the physical database whose time is less than the time point, and back to consistency condition at the time point.Parallel recovery is based on page number mode dispatching algorithm and using the framework of one log-reading thread and multi redo thread, ensuring the log records on one page redoed by a thread, multi redo threads run parallelly. It can make full use of the I/O capability of the system to shorten recovery time.Experiments show asynchronous checkpoint can improve the throughput and shorten response time. Parallel recovery can use the ability of system I/O to shorten recovery time. |
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