When a new system needs to be implemented in an organization, there are three different ways to adopt this new system: the big bang adoption, phased adoption and parallel adoption. In case of parallel adoption the old and the new system are running parallel, so all the users can get used to the new system, and meanwhile do their work using the old system. Phased adoption means that the adoption will happen in several phases, so after each phase the system is a little nearer to be fully adopted. With the big bang adoption, the switch between using the old system and using the new system happens at one single date, the so-called instant changeover of the system. Everybody starts to use the new system at the same date and the old system will not be used anymore from that moment on.