1.1.5 - Evaluate alternative installation processes. Flashcards
Name the 4 methods of system conversion.
1) Direct change-over / Big Bang / Immediate
2) Parallel running
3) Pilot running
4) Phased running
Describe how direct change-over happens.
The new system and is implemented the and the old system is immediately discontinued.
Explain the costs and risks of direct change-over.
Low cost as only one system needs to be maintained at once.
High risk as the new system may not function as expected.
What 3 things must be true for a direct change-over to be possible?
1) The system being replaced is non-critical.
2) Appropriate training has taken place beforehand.
3) All new procedures are in place.
Define parallel running.
When both systems run at the same time for short period.
Why is parallel running a popular type of system conversion?
It reduces risk and provides a higher degree of protection from failure because if the new system fails the company can revert to the old system.
Explain the cost of parallel running.
The large costs are due to the duplication of facilities and requirement of personnel to maintain the dual systems.
What should be decided before a parallel running system conversion occurs?
A target date for the old system to be discontinued.
What is pilot running?
A type of system conversion where the implementation of the new system takes place section by section, e.g. first installed in one sales region, then more widely if successful.
Give 3 benefits of pilot running.
1) Risk of failure is localised.
2) Problems can be rectified before wide distribution.
3) Other personnel can be trained before wide implementation.
What is the main drawback of pilot running?
Conversion period is very lengthy and is not always feasible.
Define phased running.
A type of system conversion where one module of the system is converted at a time.
Give 2 benefits of phased running.
1) Rate of change can be minimised.
2) Data processing resources can be acquired gradually.
Give 2 drawbacks of phased running.
1) There is an extended training period, and adoption of the new system takes longer as each phase is implemented separately.
2) Costs are increased to develop temporary interfaces with old systems.
