Data Synchronization Schemes for Multiple Copied Data Bases.

摘要

In the network environment with distributed multiple-copied files, a lockout mechanism is required to guarantee the data synchronization. File access requests from geographically dispersed computer nodes have to be coordinated to maintain consistency of multiple-copied files. The advantages of a multiple-copied file in a loosely coupled computer communication network are its reliability to partial network failures and good response to real time file manipulation. In this report, the fundamental problems relating to the lockout synchronization of a multiple-copied file are presented from a new point of view. It can be shown that the file lockout state of the distributed multiple copes is an inherent characteristic of the file manipulation operations. The objective of this work was to determine the performance of data synchronization techniques in the maintenance of distributed multiple-copied files in a computer network using G.P.S.S. simulation. The system visualized is a set of identical copies of a file residing in nodes that form a computer network. Each file is supervised by a Local File Manager (L.F.M.) which is under a control scheme to maintain the congruency and consistency of these files by synchronizing the file access and updating information. This is achieved by locking out the file copies once an L.F.M. was granted the right of updating a file for a particular user. (Author)