The parallel deployment is used even after it is
expensive because:
- The new and old systems run together for a given period of time
which provides the users with time to learn the new system while
keeping their old system handy and available.
- This is the method which has lowest risk.
- If anything goes wrong at any point there is a possibility of
reverting the entire system to its original state which provides
safety against anything wrong.
The Phased deployment is used even after being expensive
because:
- The new system is implemented in phases which provide an
opportunity for the users to learn by taking their time.
- Since it is implemented in phases if anything goes wrong it
only affects a small part of the business.
- The Information Technology team is under less burden and
pressure under this process.