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Migrating Legacy Systems: Gateways, Interfaces and the Incremental Approach
     

Migrating Legacy Systems: Gateways, Interfaces and the Incremental Approach

by Michael L. Brodie, Michael Stonebraker
 

ISBN-10: 1558603301

ISBN-13: 9781558603301

Pub. Date: 11/15/1994

Publisher: Elsevier Science & Technology Books

Many businesses are burdened by legacy ISs--existing systems that contain valuable data but lack the power or the agility to meet current organizational requirements. Since such systems are by nature resistant to modification, the only way an enterprise can gain full use of the data within one is to move to a completely new IS--ideally, one that won't become a

Overview

Many businesses are burdened by legacy ISs--existing systems that contain valuable data but lack the power or the agility to meet current organizational requirements. Since such systems are by nature resistant to modification, the only way an enterprise can gain full use of the data within one is to move to a completely new IS--ideally, one that won't become a legacy itself in a few years. This book discusses the challenges and provides a framework for a workable system migration, based on incremental modifications that allow the manager to control cost and risk. Focusing on data migration, the authors outline key techniques for transforming a legacy IS into a flexible system that meets current needs and is adaptable to unpredictable future changes.

Because designing, developing, testing, and deploying a new system all at once would be extremely risky, the authors advocate a step-by-step strategy that migrates the system to a decomposable target environment while the current IS remains completely operational. Their flexible 11-step method allows any IS to be migrated incrementally, using gateways to access data reliably and accurately without any downtime.

Because each company's IS is as unique as its business strategy, the authors focus on the choices and pitfalls that may be encountered in an IS migration. Drawing on over 45 years of collective IS experience, they illustrate their work with two complete case studies of migration projects they worked on themselves. Their versatile solution is effective for any migration, including those to a client/server environment using relational DBMSs and 4GLs.

Features a special survey of migration tools by Jennifer Schmidt.

Note: the authors would be very interested in receiving a brief report on any successful legacy IS migration project using their methodology or any other, or of significant problems encountered in a migration attempt. As such projects take years, success can apply to the first significant increment. Please send reports by e-mail to Michael L. Brodie (brodie@gte.com) and Mike Stonebraker (mike@nobozo.CS.Berkeley.EDU)or via regular mail to:

Michael L. Brodie
GTE Laboratories Incorporated
40 Sylvan Road, MS-62
Waltham, MA 02254 USA

Product Details

ISBN-13:
9781558603301
Publisher:
Elsevier Science & Technology Books
Publication date:
11/15/1994
Series:
Morgan Kaufmann Series in Data Managemen
Pages:
191
Product dimensions:
7.47(w) x 9.24(h) x 0.74(d)

Table of Contents

Migrating Legacy Systems: Gateways, Interfaces & The Incremental Approach by Michael L. Brodie and Michael Stonebraker
    Foreword by Blayne Maring
    Preface
    1 Problems and Possibilities of Legacy Migration
      1.1 The Legacy IS Problem
      1.2 More About Legacy ISs
      1.3 The Solution: Migration
      1.4 About the Term Migration
      1.5 Migration Strategies
        1.5.1 The Cold Turkey Approach
        1.5.2 The Chicken Little Alternative
      1.6 Migration Complexity and IS Architectures
        1.6.1 Decomposable Legacy IS Architectures
        1.6.2 Semidecomposable Legacy IS Architectures
        1.6.3 Nondecomposable Legacy IS Architectures
        1.6.4 Discussion
      1.7 The Role of Gateways
      1.8 Interface Migration
      1.9 Preparation and Global Design
      1.10 The Chicken Little Steps
        Step 1: Incrementally Analyze the Legacy IS
        Step 2: Incrementally Decompose the Legacy IS Structure
        Step 3: Incrementally Design the Target Interfaces
        Step 4: Incrementally Design the Target Applications
        Step 5: Incrementally Design the Target Database
        Step 6: Incrementally Install the Target Environment
        Step 7: Incrementally Create and Install the Necessary Gateways
        Step 8: Incrementally Migrate the Legacy Database
        Step 9: Incrementally Migrate the Legacy Applications
        Step 10: Incrementally Migrate the Legacy Interfaces
        Step 11: Incrementally Cut Over to the Target IS
      1.11 Cutover
      1.12 Version Control and Configuration Management
      1.13 Preventing New Legacy ISs
      1.14 Closing Remarks

    2 Migrating Decomposable Legacy ISs
      2.1 Decomposable Architectures and Chicken Little
      2.2 Forward Migration method
        Step 1: Incrementally Analyze the Legacy IS
        Step 2: Incrementally Decompose the Legacy IS Structure
        Step 3: Incrementally Design the Target Interfaces
        Step 4: Incrementally Design the Target Applications
        Step 5: Incrementally Design the Target Database
        Step 6: Incrementally Install the Target Environment
        Step 7: Incrementally Create and Install the Forward Database Gateway
        Step 8: Migrate the Legacy Database
        Step 9: Incrementally Migrate the Legacy Applications
        Step 10: Incrementally Migrate the Legacy Interfaces
        Step 11: Incrementally Cut Over to the Target
      2.3 Reverse Migration Method for Deomposable Legacy ISs
        Step 7: Incrementally Create and Install the Reverse Database Gateway
        Step 8: Incrementally Migrate the Legacy Applications
        Step 11: Incrementally Cut Over to the Target IS
      2.4 General Migration Method
        Step 5: Incrementally Design the Target Database
        Step 7: Incrementally Create and Install the Database Gateway
        Step 8: Incrementally Migrate the Legacy Database
        Step 9: Incrementally Migrate the Legacy Applications
        Step 11: Incrementally But Over to the Target
      2.5 Closing Remarks

    3 Case Study 1: Migrating Money Central�s Cash Management System
      3.1 Our Background Research
      3.2 Analysis of the CMS Core
      3.3 The CMS Migration Plan
      3.4 CMS Cutover Issues
      3.5 Closing Remarks

    4 Migrating Semidecomposable Legacy ISs
      4.1 Semidecomposable IS Migration Method
        Step 1: Incrementally Analyze the Legacy IS
        Step 2: Incrementally Decompose the Legacy IS Structure
        Step 3: Incrementally Design the Target Interfaces
        Step 4: Incrementally Design the Target Applications
        Step 5: Incrementally Design the Target Database
        Step 6: Incrementally Install the Target Database
        Step 7: Incrementally Create and Install the Application Gateway
        Step 8: Incrementally Migrate the Legacy Database
      4.2 The Remaining Steps: Application Migration, Interface Migration, and Cutover
      4.3 Closing Remarks

    5 Case Study 2: Migrating Global Telecom�s Telephone Provisioning System
      5.1 Some Basic Information
      5.2 Analysis of TPS
      5.3 The TPS Migration Gateway
      5.4 The TPS Migration Plan, Part I
      5.5 TPS Migration History

    6 Migrating Nondecomposable Legacy ISs
      6.1 The Migration Method
        Step 1: Incrementally Analyze the Legacy IS
        Step 2: Incrementally Decompose the Legacy IS Structure
        Step 3: Incrementally Design the Target Interfaces
        Step 4: Incrementally Design the Target Applications
        Step 5: Incrementally Design the Target Database
        Step 6: Incrementally Install the Target Environment
        Step 7: Incrementally Create and Install the IS Gateway
        Step 8: Incrementally Migrate the Legacy Database
        Step 9: Incrementally Migrate the Legacy Applications
        Step 10: Incrementally Migrate the Legacy Interfaces
        Step 11: Incrementally Cut Over to the Target IS
      6.2 Closing Remarks

    7 Migrating Legacy ISs: A General Case
      7.1 Architecture Notes
      7.2 The General Case
        Step 1: Incrementally Analyze the Legacy IS
        Step 2: Incrementally Decompose the Legacy IS Structure
        Step 3: Incrementally Design the Target IS
        Step 4: Incrementally Install the Target Environment
        Step 5: Incrementally Migrate
      7.3 The TPS Migration Plan, Part II
      7.4 Closing Remarks

    8 Distributed Computing and Incremental Migration
      8.1 Supporting Technologies
        8.1.1 CORBA
        8.1.2 OLE/COM
        8.1.3 Distributed Databases
        8.1.4 Transaction Monitors
        8.1.5 Combined Architecture
        8.1.6 The Horse Race
      8.2 Distributed Computing Principles
        8.2.1 Object Orientation
        8.2.2 Openness and Standards
        8.2.3 The Enterprise Information Architecture
      8.3 Distributed Database Architectures
      8.4 CORBA Architectures
        8.4.1 Chicken Little Migration on a CORBA Architecture
        8.4.2 CORBA-Based Application Integration and Migration Frameworks
      8.5 Closing Remarks

    9 Tool Wish List
      9.1 Gateways
      9.2 Specification Extractors
      9.3 Application Analyzers
      9.4 Dependency Analyzers
      9.5 Migration Schema Design and Development Tools
      9.6 Database Extractors
      9.7 Higher-Level 4GLs
      9.8 Distributed Systems Design and Performance Testing
      9.9 Application Cutover
      9.10 Distributed IS Development and Migration Environment
      9.11 Migration Planning and Management
      9.12 More Information on Tools

    10 A Practical Implementation with Migration Tools by Jennifer Schmidt
      10.1 Using Tools
        10.1.1 Future Directions
      10.2. Tool Categories
        10.2.1 Gateways
        10.2.2 Analyzers and Specification Extractors
        10.2.3 Migration Tools
        10.2.4 Testing
        10.2.5 Configuration Management Tools
        10.2.6 Full-Service Migration Consultants
      10.3 Tools and the Chicken Little Steps
      10.4 Migration Management
      10.5 Getting Started
    Glossary
    References
    Index
    About the Authors

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