| Description |
1 online resource (152 pages) |
| Contents |
Cover; FM; Table of Contents; Preface; Chapter 1: Definition, Issues, and Strategy; What is Legacy?; An IT-Centric View of the World; Systems Development in Context; Systems Development Scaled with Time; Examples of Real Legacy Systems; Common Issues; No Documentation; Lost Knowledge; Hidden Knowledge; Unused Functionality; No Coherent Design/Inconsistent Implementation; Fragility (versus Stability); Tight Coupling; Loose Coupling; Zombie Technologies; Licensing; Regulation; Politics; Organization Constraints and Change are Reflected in the System |
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External Processes Have Evolved to Fit around the SystemExternal Systems Have Evolved to Fit around the System; Decaying Data; Now What?; Reasons to be Cheerful; A Legacy System is a Successful System; You Have Real Users You Can Talk To; You Can Learn a Lot about the Business; You Can Have a Large Impact Quickly; It's Important, But Not Trendy, So You'll Get Paid Well!; Strategies; Ignore It; What is it?; Investigation; Maintenance; Upgrade; Migration; Incremental Improvements; Replacement; A Special Note on Decommissioning; Conclusion; Chapter 2: Investigation and System Review |
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Architectural Description and ReviewStakeholders; Locate the stakeholders; End Users; Support Staff; System's Infrastructure Staff; Audit and Compliance; Budget Holders; Third-Party Suppliers; Developers/Software Engineers/Database Analysts; Document the Stakeholders; Architectural Sketches; Why Sketch?; Context Diagram; Container Diagram; Component Diagram; C4 -- Classes; Further Analysis; What Else Can Be Done?; Further Static Analysis; Further Dynamic Analysis; Security Considerations; Passwords; Account Maintenance and Life cycle; Cryptographic Keys; Certificates |
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Third-Party Passwords and KeysLack of Patching; Moving from Closed to Open Networks; Modernizing Data Formats; New Development and Copied Data; Server and Infrastructure Consolidation; Improved Backup Processes; Checklist of Questions and Actions; Chapter 3: Making Changes; Safely Making Changes; Virtualization Is Your Friend; 50,000-Foot View of the Virtualization Process; Actions to Make a System Safe to Change; Preparation Issues; External Dependencies Required for Testing; Duplicate Test System Data Becomes Stale Quickly; Internal Coupling Stops You Swapping Components |
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Changes Cause Unexpected ErrorsLicensing and Regulation Issues Running Multiple Copies; Structural Changes for Disaster Recovery/High Availability; Stabilization; Why Stability?; What Have We Achieved Already?; Bad Data; Removing Unwanted Data; Data Cleansing; Removing Unneeded Components; Removing Unneeded Tasks; Process Cleansing; Removing Unused User Options; Don't Underestimate a Resource Boost; Re-Examine your Application Settings; Optimize the Users' Actions; Leaving a Good Legacy; Why Bother Leaving a Good Legacy?; Documentation; Tests; Design Considerations; Appendix A: Example Legacy Scenario. |
| Summary |
The IT industry is obsessed with new technologies. Courses, books, and magazines mostly focus on what is new. Starting with what a legacy system looks like to applying various techniques for maintaining and securing these systems, this book gives you all the knowledge you need to maintain a legacy system. |
| Local Note |
eBooks on EBSCOhost EBSCO eBook Subscription Academic Collection - North America |
| Subject |
Software reengineering.
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Software maintenance -- Management.
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Computer architecture.
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Electronics engineering. |
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Information technology: general issues. |
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Internet: general works. |
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Computer science. |
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Computers -- General. |
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Computers -- Internet -- General. |
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Computers -- Computer Engineering. |
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Computer architecture |
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Software maintenance -- Management |
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Software reengineering |
| Other Form: |
Print version: Annett, Robert. Working with Legacy Systems : A Practical Guide to Looking after and Maintaining the Systems We Inherit. Birmingham : Packt Publishing, Limited, ©2019 9781838982560 |
| ISBN |
1838988572 |
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9781838988579 (electronic bk.) |
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