This is an interesting time.... the implementation stage has been reached.  The system has been developed and tested.  It is working correctly and doing everything that was agreed during the design stage.  The business is waiting in eager anticipation for the new system to be handed over to them.

The key events in this stage are:

DATA CONVERSION

Data stored in files on the old system are now converted into the correct format for the new system.

SYSTEM CHANGE-OVER

Now it is time to switch off the old system and turn on the new.

It sounds simple, but  most of the time it isn't!

What are the alternatives?

1) Switch off the old system and switch on the new.

Of course, this is the simplest scenario!  All the workers are waiting for the fabulous new system to come 'on -line' but as the minutes tick by,  a new customer has just ordered a holiday / medical operation / flight / mortgage.

How do you deal with these last-minute (but vital) clients?

Answer: You must deal with last  minute changes and accept that there may be some upheaval and mistakes made in the short term.

2) You run the old and new system in parallel for a time.

A popular method compared to the switch off / switch on approach. After all, the customer does not care what your IT system is made up of - they are only (rightly) concerned with their holiday / medical operation / mortgage etc being booked correctly.

And so,  a popular method is to allow the old system to run alongside the new one. Then in the quiet period (say overnight) , the new system absorbs all the old system's information. By the next morning, the system is fully loaded and ready to go.

3) You run only part of the new system

This is the 'phased approach' to system testing. Imagine a system so sensitive to change that only a very careful change can be considered.

Example: A new air traffic control system.

Neither of the other two approaches would be suitable for such a critical system.

TRAINING

It is at the implementation stage that staff training takes place.  Staff need to be shown how to use the new system and how to access help should they run into difficulties.  There may be member of the development team on call for a short period of time or there may be a dedicated help line that staff can ring to get answers. 

There will most definitely be a user manual to act as a source of reference.