A good project management team understands this and ensures that each of these elements is correctly attended to. All of these elements are needed to ensure the success of any Oracle Financial project, be it a new installation, upgrade or the addition of custom code.
Many of the mistakes that are made occur, not because of bad practice, but because there is an unexpected pitfall. This is why it is very useful to have a project manager that has been through this process before and has seen the problems that occur between, for instance, 11.5.8 and 11.5.10. The implementation of the product will be far smoother when these pitfalls are avoided.