Changing Cost Center / Profit Center asignment to a different group

Hi

I want to change the assignment of some of our cost Centers to different groups in the hierarchy. I know that the data already posted to CC/PC moves to the new group for reporting. I just wanted to take another opinion if anyone of you had done this before and had faced any issues. We are doing this during mid year.

Also what is the exact use of Alternative hierarchy fields 1 & 2 in T Code OKKP

Thanks in advance