TOPIC: Why do we need Change , Requirement plans ?

Hello All,

I was reading RMC and came across that apart from the Plans for each of the KAs, there are plans for Change, Requirement, Configuration & Process improvement plans.

Though I can rationalize the need of Configuration & Process Improvement plans, but not able to understand why and in what circumstances do we need Change & Requirement Plans. Why the same cannot be planned in Scope Management Plan ?

Your answers would be appreciated