Research On Log Management System And Implementation In Oscar

As an important branch of computer soft wares, Database Management System is a complex one. DBMS is a powerful tool to manage mass data very efficiently. Database Management System is used to provide duration storage, programming interfaces and the ability to manage transaction.In order to maintain the consistency and integrity of data in DBMS, DBMS uses redundant data during running. Backup and logging are two main methods. As a large scale Object-relational database management system, OSCAR also provides these two methods. OSCAR's Logs record the updates of the DBMS in a safe way and are used in system recovery.This dissertation does some research on log management, transaction management and recovery methods of DBMS. After studying of all these aspects, this dissertation describes a safe and efficient model of log management system.This dissertation focuses on the design and implementation of OSCAR's log management module. This module is in charge of the form and organization of the log record, log page and log file. This module is also used to control the concurrent access of the log records and provides rapid read/write to the upper level.The design of the log management module reflects high efficiency and extension of the system. From the form of log to the strategy of concurrency control, log management module focus on the elevation of concurrency.Moreover, by choosing different kinds of write-back strategy, log management system can cooperate with buffer management to implement commit delay and group commit. Through these methods, DBMS can run more efficiently.Log management module supports the concepts of log member and log group. During system running time, we can add or delete the log group and log member. The system also implements the recycle of log groups. OSCAR's log management module also supports the archive of on line log group. When the on line log group is ruined, OSCAR can use the archived log group in system recovery.Moreover, OSCAR's log management module takes advantage of some methods to organize log records referred in ARIES, such as the concept of LSN. The reason why we use this method is that the recovery module of OSCAR adopts the framework referred in ARIES. When OSCAR meets a failure in running, recovery module can work conveniently using the logs recorded by log management module.