Dive into this list of the top FAQ's on SAP S/4HANA Finance.
Is merging of actuals & plan into ACDOCA versus ACDOCP? Is the planning data going to go to ACDOCA or ACDOCP? If we copy actual to plan for each monthly forecast version, will the P table end up with 12 times the records of the A table?
Planning data will update to ACDOCP. In your copy function you would have to decide at what aggregation you updated ACDOCP (1:1 or roll-up e.g. production orders to not have quite so much data in your forecast).