Software Maintenance

Software Maintenance

1. The modification of a software product after delivery to correct faults, to improve performance or other attributes, or to adapt the product to a modified environment

2. Type of Maintenance

   • Corrective Maintenance
     • Identify and remove defects
     • Correct actual errors
   • Perfective Maintenance
     • Improve performance, dependability, maintainability
     • Update Documentation
   • Adaptive Maintenance
     • Adapt to a new environment e.g Hardware, OS, Middleware
     • Incorporate new capability
   • Preventive Maintenance
     • Identify and detect latent faults
     • System with safety concerns
   • Emergency Maintenance
     • Unscheduled corrective maintenance

3. Maintenance cost factors

   • Team stability
     • Maintenance costs will reduced if the same staff are involved with them for some time
   • Contractual Responsibility
     • The developers of a system may have no contractual responsibility for maintenance so there is no incentive to design for future change
   • Staff skill
     • Maintenance staff are often inexperienced and have limited domain knowledge.
   • Program age and sturcture
     • Structure is degraded and they become harder to understand and change.

4. Maintenance Prediction

   • assessing parts of the system may cause problem
   • Assessing parts of the system may have high maintenance costs

5. Chance Prediction

   • Understand the system and its environment
   • Understand the relationships between a system and its environment

6. Complexity Metrics

   • Complexity of control structures; Complexity of data structures; Object, method (procedure) and module size.

7. Process metrics

   • Number of requests for corrective maintenance
   • Average time required for impact analysis
   • Average time taken to implement a change request
   • Number of outstanding change requests

8. Evolution processes

   • The type of software being maintained; The development processes used; The skills and experience of the people involved

9. Change implementation

   • Proposed changes - requirements analysis - requirements updating - software development

10. Emergency Repair

    • Change request - Analyse source code - modify source code - deliver modified system

11. System re-engineering

    • Re-structuring or re-writing part or all of a legacy system without changing its functionality
    • The system may be re-structured and re-documented

12. Advantages of reengineering

    • Risk : development problems, staffing problems and specification problems
    • The cost of re-engineering is often significantly less than the costs of developing new software

13. Reengineering process activities

    • Source code translation
    • Reverse engineering
    • Program structure improvement
    • program modularization
    • Data reengineering

14. Reengineering cost factors

    • The quality of the software to be reengineered.
    • The tool support available for reengineering.

15. Legacy system evolution

    • Separation between software development and software maintenance is unhelpful.

16. Legacy system categories

    • Low quality, low business value
    • Low-quality, high-business value
    • High-quality, low-business value
    • High-quality, high business value

17. Business value assessment

    • System end-users;
    • Business customers
    • Line managers
    • IT managers
    • Senior managers

18. System quality assessment

    • Business process assessment
    • Environment assessment
    • Application assessment