1. Direct changeover

The old system is stopped completely and the new system is started. All of the data that used to be input into the old system is now input into the new one.

Advantages:

• • Takes minimal time and effort.

  • The new system is up and running immediately.

Disadvantages:

• • If the new system fails, there is no back-up system. Thus there

  • could be significant downtime while the system is being fixed.

2. Parallel running

The new system is started, but the old system is kept running in parallel (side-by-side for a while. All of the data that is input into the old system, is also input into the new one. Eventually, the old system will be stopped, but only when the new system has been proven to work.

Advantages:

• • If anything goes wrong with the new system, the old system will act as a back-up.

  • The outputs from the old and new systems can be compared to check that the new system is running correctly.

Disadvantages:

• • Entering data into two systems and running two systems together takes a lot of extra time, expense, and effort.

3. Phased implementation

The new system is introduced in phases (stages, or steps), gradually replacing parts of the old system until eventually, the new system has taken over. Step by step, technical sub-parts of the new system replace the old ones, until the entire system has been replaced.

Advantages:

• • Allows users to gradually get used to the new system.

  • Staff training can be done in stages.

Disadvantages:

• • If a subpart of the new system fails, there is no back-up for that subpart of the system. Thus there could be significant downtime until a solution is found.

4. Pilot running

The new system is first of all piloted (trialled) in one part of the business / organization (e.g. in just one office or department). In other words, one department of the business is given full implementation of the new system, similar to a “trial version” of the system.

Once the pilot system is running successfully, the new system is introduced to the rest of the business / organization.

Advantages:

• • All features of the new system can be fully trialled.

  • If something goes wrong with the new system, only a small part of the organization is affected.

  • The staff who were a part of the pilot scheme can help train other staff.

Disadvantages:

• • For the office/department doing the pilot, there is no back-up system if things go wrong.

  • Though the pilot may be successful, there is still a possibility that the system may not be capable of handling its full-scale requirements.