Implementation in  SDLC Model.

There are several types of adoption can be used to implement a system. The types ‘Big bang’ or "Direct" , ‘Parallel Run’ and ‘Phased adoption’ form the main types that are used to implement a system

Big Bang or Direct :With this method of implementation the users stop using the old system and start using the new system from a given date.The big bang relates to the cosmological theory (Big bang) where the start of the cosmos happened at one moment in time.

Parallel Run:the new system is introduced alongside the existing system. With parallel running both systems will be in operation at the same time.

Phased Adoption means that the adoption will happen in several phases, so after each phase the system is a little closer to be fully adopted by the organization

Pilot adoption: The pilot adoption method is used for large organizations that have multiple locations or largely independent departments. The new system is introduced in one of the locations or departments and extended to other locations or departments over time The advantage is that and 'damage' is minimized, and the pilot group can help exert pressure on other groups that may be resistant to change.

The actual selection is done by prioritizing the goals to be achieved and then matching a strategy against it (Eason, 1988).

Once the management has decided to use the big bang method and supports the changes which are needed for this, the real changing process can start. This process consists of several steps:

1.converting the system

2.Release the system

~ Release converted database
~ Release produced application
~ Release infrastructure

3.Prepare users

~ Maintain buffer of experienced staff
~ Train users

This sudden changeover is quite drastic. This has advantages, but because of the instant changeover there are also disadvantages (Koop, Rooimans and de Theye, 2003).

The advantages of this method: 1.Training is only needed for the new method, not also for the changeover period. 2.User documentation does not need to be updated during the implementation process, because it happens in such a short period. 3.The changeover is at one date and this date is clear for everyone. 4.There are no special interfaces needed to be able to get used to the new system, because the new system is all there is.

The disadvantages of this method: 1.There is no time for extra additions 2.The completeness and validity of the converted data is not completely proved, only in the pre-phases, but not in the whole system situation. 3.Start up problems are a problematic factor. 4.The operation is complex, one of the main complexities is tuning all activities to happen on one moment: the big bang 5.‘Fall back’-plans are hard to develop and become more impossible when the big bang has taken place 6.This adoption is vulnerable because of the limited possibilities to maneuver. There is a lot of pressure because the deadline must be met.

Parallel Run

The activities in Parallel Run are divided in five main phases:

1.Define implementation strategy: that deals with the kind of implementation strategy should be executed. 2.Pre-implementation: which has to do with constructing a planning of all aspects and requirements involved in the implementation. 3.Prepare organization: The organization should be prepared properly according to the previous phase. 4.Conversion: Deals with the actual conversion process. 5.Closing the conversion process: proceeding with the new system.

Disadvantages:

The reason for an organization to choose for parallel adoption in favour of a pilot conversion, big bang or phased adoption is often a trade-off between costs and risk (Andersson, Hanson, 2003). Parallel adoption the most expensive adoption method (Chng, Vathanopas, 2002, Microsoft, 2004, Anderson et al., 2003), because it demands from the organization that two systems run parallel for a certain period. Running two systems simultaneously means that an investment in Human Resources has to be made. Besides a good preparation of the (extra) personnel, that has to go through a stressful period of parallel running where procedures cross each other. (Rooijmans, 2003, Eason, 1988) Efforts should be placed on data-consistency and preventing data corruption between the two systems. (Chng et al. 2002, Yusuf, 2004 ) Not only for the conversion process itself, but also in training them for handling the new system.

Advantage: Parallel Run minimizes the risk of major flaws in the new system causing irreparable harm to the business.

Phased Adoption

The phased approach takes the conversion one step at a time. The implementation requires a thoroughly thought out scenario for starting to use the new system. And at every milestone one has to instruct the employees and other users. The old system is taken over by the new system in predefined steps until it is totally abounded. The actual installation of the new system will be done in several ways, per module or per product and several instances can be carried out. This may be done by introducing some of the functionalities of the system before the rest or by introducing some functionalities to certain users before introducing them to all the users. This gives the users the time to cope with the changes caused by the system.

Advantages of Phased Adoption 1.The conversion will be done in parts. Time is available for adjustments 2.Negative influences that arise at the start are less critical 3.No ‘catch-up’ period is needed. 4.Time for the users to adapt is longer 5.Technical staff can concentrate on part of the system or some of the users.

Disadvantages of Phased Adoption 1.Several adjustments are needed 2.Training sessions are confusing for users as they are asked to work with the new and the old system 3.Several changes in documentation 4.The duration of the project 5.System delivery milestone is unclear 6.Correctness and completeness of the dataset has to be checked several times 7.A ‘fall back’ to the old system is becoming more difficult every new phase. 8.The implementation may appear unclear to the employees and other users.