(3) The scalability of the system is always limited.
When environment or needs of the application have great
changes, the original design may eventually no longer be
able to be expanded, must reinvent the wheel. Then it will
start a new life cycle of database design. However designers
should be fully taken into account the existing applications
in the process of a new design. It should make the user have
a smooth transition from the old system to the new system
as far as possible.