I am going to write a more full featured post about this, but I think that the jotted notes for that are also interesting.

Big rafactoring is what I call to a refactoring that touces large swaths of the code base, changing the implementation of a core service is one such example, or changing key archtictual patterns.

• Must have tests at first.
• Change is too big, will affect too much of the system to change in place.
• Can't change the system and the test at the same time
• Taking as granted that you have source control.
• Ability to rollback at any time.
• Tests are hindarance, not a help.
• Stateful structure with tests.