Design and Implementation of a Module to Synchronize Databases

Design and Implementation of a Module to Synchronize Databases

Amit Hingher

Reviewers: Prof. Dr. rer. nat. habil. Andreas Heuer Prof. Dr.-Ing. Hartmut Pfüller

Advisor: Dr.-Ing. Holger Meyer

Herr Andreas Finger

Stefan Dummann (softEnergy GmbH)

Master Thesis, University Of Rostock, Germany

23rd May 2007

Master Thesis, Amit Hingher 2

Overview

Introduction

Concept

WIS-Sync - A Prototype

Conclusions & Future Work


1. Introduction

Data Replication

Wind Information System (WIS)

Motivation

Existing Solution


What is Data Replication? Database replication:

Process of creating and storing multiple copies of a database with the same data in different locations.

Two types of replication- Synchronous Asynchronous


Data Synchronization Synchronization / Merge replication

Keeps the data in two or more locations up-to-date so that each repository contains identical information.

Copies data in both directions Used for disconnected environment


WIS - Wind Information System

An innovative solution for complex analyses and monitoring of power plant data received from energy plants

GUI is provided by a Web server and can be accessed by client through a Web-Browser like IE or Mozilla

Diverse databases running on the server and client i.e. Oracle, Sybase, MySQL

Communication only possible between server and remote replicas and no “inter-replica” communication


Motivation

LocalcopyWIS

Server

Localcopy

No communication link

Synchronize


System Overview


Existing SolutionWIS


Why another solution ? Dumping whole DB to client

Alternative to log based capture – A middle-ware replication tool that intercepts

command stream between application and database

Synchronization tool relies entirely on transaction log

Cost of maintenance

Currently no manual interaction


2. Concept Proposed System

WIS-Sync: A 3-Step Process

Capture process

Merge Process - Conflict Resolution

Table Filtering

Incremental progress

Manual resolution


WIS-Sync: A 3-Step Process


Golding’s Timestamp Anti-Entropy Protocol Updates are propagated via anti-entropy

sessions in which two replicas exchange the content of their logs


WIS-Sync: Capture Process


Conflict Resolution - Basics A conflict is said to arise when rows with

same unique ID from the same tables are updated on different databases

Resolution option used: Server- Wins Client-Wins


Conflict Scenario - 1

Insert – Insert



Update - Delete



Update-Update


WIS-Sync: Merge Process


Table-Filtering

Allows user to select the tables he wants to synchronize

Provides maximum flexibility

User has full control over the system thus avoiding any unnecessary updates


Incremental Progress


Violations – An Example


How has this research helped ? Features & Improvements

Capture Process - “direct-to-database” method Table filtering Conflict Resolution Incremental progress Manual resolution Support for heterogeneous databases


3. WIS-Sync : A Prototype


OJB – ObJect Relational Bridge Apache (OJB) is an Object/Relational mapping tool that allows transparent persistence for Java Objects against relational

databases.

Supports the following DB’s: MSSQL MySQL Oracle MS Access PostgreSQL Informix Sybase MaxDB


O/R Mapping


WIS-Sync: Class Diagram


WIS-Sync: Configuration Page


3. Conclusions

No general solution available toward synchronization

Principal goal of an update propagation strategy is to ensure internal and mutual consistency

“Direct-to-database” approach can prove to be an alternative to log-based capture

O/R Mapping can be used in scenarios where compatibility between diverse databases is needed.


Future Work

User-friendly GUI Interface

Multiple users synchronizing

Could be implemented for a mobile as well.


Thank you all !!!

Design and Implementation of a Module to Synchronize Databases

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