Implementation Methods
When a new system replaces an old one, the changeover method determines how the switch happens. Each method balances risk, cost, and disruption differently.
Learning Objectives
- 12.5.2.1 Compare changeover methods: direct, phased, parallel, pilot
Conceptual Anchor
The Road Replacement Analogy
Replacing an old road with a new one can be done in different ways: Direct = close the old road, open the new one at once. Parallel = keep both open until the new one is proven. Phased = replace one section at a time. Pilot = test the new road in one neighborhood first.
Rules & Theory
Changeover Methods
| Method | How It Works | Advantages | Disadvantages |
|---|---|---|---|
| Direct (Big Bang) | Old system switched off, new system switched on immediately | Fastest, cheapest, no duplication | Highest risk — if new system fails, no fallback |
| Parallel | Both old and new systems run simultaneously until new one is proven | Safest — can fall back to old system | Most expensive — double running costs, staff overload |
| Phased | New system introduced one module/feature at a time | Lower risk per phase; errors contained to one module | Slow; old and new must work together during transition |
| Pilot | New system tested in one location/department first, then rolled out | Real-world testing before full deployment | Pilot site may not represent all use cases |
Choosing the Right Method
| Scenario | Best Method | Why |
|---|---|---|
| Hospital patient records system | Parallel | Cannot afford data loss; lives at stake |
| Small company upgrading email | Direct | Low risk, simple system, fast switch |
| Bank replacing ATM software nationwide | Pilot | Test in one city first, fix issues, then roll out |
| School introducing new modules in an LMS | Phased | Add one subject at a time; train staff gradually |
Exam Tip
When asked to recommend a method, always justify with the specific context. Mention risk level, budget, system complexity, and how critical the system is.
Common Pitfalls
Confusing Phased and Pilot
Phased = modules/features one at a time (entire organization). Pilot = entire system in one location/department first. Phased is about what, pilot is about where.
Tasks
Name and define the 4 changeover methods.
Why is parallel changeover the safest but most expensive method?
A national chain of 200 pharmacies wants to replace their inventory system. Recommend a changeover method and justify your choice.
Self-Check Quiz
Q1: What is the riskiest changeover method?
Q2: What is the difference between phased and pilot?
Q3: When would you use parallel changeover?