The best place for you to start is to review E04.05 Integrated Change Control from The PM PrepCast. Here we look at various aspects of change control, including CMS. That will make things clearer for you.
Am not able to understand what behind Configuration management plan? In PmBok stated:
Configuration management plan. The configuration management plan defines those items
that are configurable, those items that require formal change control, and the process for
controlling changes to such items.
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