The act of "going into production" is not simply turning on a switch that says now the application is production-ready. It is much more complicated than that. And from one project to the next, the way in which a program goes into production can change.

In some cases, where we have an existing system that we are replacing, we might decide to run in parallel for a period of time prior to switching over to the new application. In this case, we run both the old and the new systems against the same data and then compare the results. If after a certain period of time we are satisfied with the results, we switch to the new application. If we discover problems, we can correct them and continue the parallel run until there aren't any new problems.

In other cases, we are dealing with a new system, and we might just have a cut-over day when we start using it. Even in the case of a new system, we are usually replacing some form of system, even if it's a manual system, so we could still do a parallel test if we wanted to.

Whichever method is used to go into production, there are still all of the loose ends that need to be taken care of before we hand the system over to Operations. One of the tasks is to provide documentation for the system, as well as procedures for running and using it. We need to train everyone who interacts with the system.

When all of the documentation and training has been done, we can hand over responsibility for the running of the application to Operations and responsibility for maintaining the application to the Maintenance group. In some cases, the Development group also maintains applications.

At this point, the application development life cycle reaches a steady state and we enter the maintenance phase of the application. From this point onward, we only apply enhancements and day-to-day changes to the application. Because the application now falls under a change control process, all changes require testing according to the process for change control, before they are accepted into production. In this way, a stable, running application is ensured for end users.