Hi Devang,
OK, if I were in your shoes I would do the following steps:
1. Historical data load stop - I believe that you have a job to load historical data from ECC to BW
2. Stop load historical data to demand planning
3. Stop job statistical forecast
4. Stop release from DP to SNP
5. Stop SNP job
6. Stop CTM job
7. Delete all transactional data in APO - forecast, STO, STR, SNP PL.Orders, CTM Pl.Orders, Stocks, etc..
8. Switch the procurement type to P - EXTERNAL PLANNING (in your case planned by ECC) for all materials. You can do this with MASSD
9. Delete all publications type created in APO (CIF transfer from APO to ECC)
10. Deactivate all integration models - t.code CFM3 you choose deactivate and you enter the APO's logical name and a range for your integration models.
You can also use CFM2, you enter just APO's logical name and then deactivate them one by one manually.
11. Delete IM with CMF7
12. As Dogboy highlighted you should run the reports ............
13. Finally you can change the MRP type from X0 to PD
14. Switch from GATP to ATP check (for sale orders).
15. Create MRP job in ECC
16. Run MRP on ECC side to regenerate the production plan
Well, hope that can help you!
Good luck.
Regards, Marius