Working with Legacy Systems : a Practical Guide to Looking after and Maintaining the Systems We Inherit.
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 s...
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| Online Access: |
Full text (MCPHS users only) |
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| Main Author: | |
| Format: | Electronic eBook |
| Language: | English |
| Published: |
Birmingham :
Packt Publishing, Limited,
2019
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| Subjects: | |
| Local Note: | ProQuest Ebook Central |
Table of 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
- 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
- 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
- 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
- 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.
