When do I need Impact Analysis?

Chapter 13 Impact analysis

The following use cases are examples of impact analysis use:

You want to change a requirement when development has already started. You want to know which objects will be impacted and which tests this implies. If the requirement was associated with a use case associated with diagrams and analysis classes implemented by components, impact analysis helps you identify which analysis, design and implementation objects will be impacted by the change
You want to delete an object, impact analysis shows which objects will be impacted by the deletion, it also indicates if this object is used by other objects or in other models, if the deletion implies the deletion of other objects that will themselves impact other objects
When you made several changes in your model and you want to consolidate it, impact analysis used with the extract dependencies feature, shows which other models will be impacted by the changes you made
You want to change the data type of a primary key column, impact analysis shows which other tables and columns are impacted by the change
You want to change the signature of a class operation, impact analysis shows which child classes override this operation