How is a new system installed, and which changeover method should be chosen?
Implementation and installation of a system, the changeover methods (direct, parallel, phased and pilot), their advantages, disadvantages and suitability, and data conversion and user training.
A CCEA A-Level Digital Technology answer on implementing and installing a system: the direct, parallel, phased and pilot changeover methods, their advantages, disadvantages and suitability, and data conversion and user training.
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What this dot point is asking
CCEA wants you to describe how a finished system is installed, to know the four changeover methods (direct, parallel, phased and pilot) with their advantages, disadvantages and suitability, and to understand data conversion and user training. Scenario questions ask you to recommend a method and justify it from the context.
Implementation and installation
Before the new system can run on real data, existing data must be converted into the new system's format (for example, exporting records from the old database and importing them, checking for errors). Users must be trained so they can operate the system, and documentation (user guide, technical manual) must be ready.
The four changeover methods
- Direct changeover. The old system stops and the new one starts immediately. Quick and cheap with no duplication, but high risk because there is no fallback if the new system fails.
- Parallel running. Old and new run side by side for a period and outputs are compared. Low risk (the old system is a fallback and a cross-check), but expensive because everything is done twice.
- Phased changeover. The new system is introduced in stages, one module or function at a time. Risk is limited to the part being introduced, but the transition takes longer and the old and new parts must interoperate.
- Pilot changeover. The whole new system runs in one branch, site or department first, then rolls out everywhere. Problems are contained to one site, but some issues only appear at full scale and the pilot site carries the early risk.
Data conversion and training
Even a perfect program fails at go-live if the data is wrong or staff cannot use it. Data conversion moves and reformats existing records into the new system and must be validated to catch corruption. User training ranges from manuals and online help to hands-on sessions, and is essential for operational acceptance, which links back to operational feasibility.
Try this
Q1. State which changeover method keeps the old system running as a fallback. [1 mark]
- Cue. Parallel running.
Q2. Give one advantage and one disadvantage of direct changeover. [2 marks]
- Cue. Advantage: fast and cheap with no duplicated work. Disadvantage: high risk, with no fallback if the new system fails.
Q3. Explain why data conversion must be validated during installation. [2 marks]
- Cue. Errors introduced while transferring or reformatting records would corrupt the live system from day one, so converted data must be checked for accuracy and completeness before go-live.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA AS 18 marksDescribe the four methods of changeover from an old system to a new one, and give one advantage and one disadvantage of each.Show worked answer →
Cover all four named methods with a matched advantage and disadvantage each.
Direct changeover: the old system is switched off and the new one switched on at once. Advantage: quick and cheap, no duplication. Disadvantage: high risk, with no fallback if the new system fails.
Parallel running: old and new run together for a period and results are compared. Advantage: low risk, the old system is a fallback and a check on accuracy. Disadvantage: expensive, because work is done twice and staff are stretched.
Phased changeover: the new system is introduced one module or part at a time. Advantage: risk is limited to the part being introduced. Disadvantage: takes longer and the old and new parts must work together during the transition.
Pilot changeover: the new system runs fully in one branch or department first. Advantage: problems are contained to one site before a wider rollout. Disadvantage: not all problems show up until the full rollout, and the pilot site carries the risk.
Markers award marks per method for a correct description plus a valid advantage and disadvantage. Mixing up phased and pilot is the usual error.
CCEA AS 14 marksA hospital is replacing the system that stores patients' medical records. Recommend a suitable changeover method and justify your choice.Show worked answer →
Recommend parallel running (or a phased approach) and justify it against the safety-critical context.
Patient records are safety critical: an error or loss of data could harm patients, so risk must be minimised. Parallel running keeps the old system live as a fallback and lets staff cross-check that the new system holds the correct records before the old one is retired. The cost of running both is justified by the danger of losing or corrupting medical data.
A phased approach (one ward or record type at a time) is also defensible, limiting exposure while migrating. Direct changeover should be rejected because it offers no fallback in a safety-critical system.
Markers reward the recommendation, a justification linked to the safety-critical, high-cost-of-failure context, and (in strong answers) the explicit rejection of direct changeover.
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Sources & how we know this
- CCEA GCE Digital Technology specification — CCEA (2016)