FICO Data Conversions clarifications

Question

Hi,
I am currently working on data conversion project. We have our FY from April to March and we are going live on June 01. I am trying to analyse the FICO objects. I have seen many conversations here but confused between balances and open items. I am trying to use ABAP programs instead of LSMW as much as possible
Master Data:
1) GL Master Data
2) AP Vendor Master Data
3) AR Customer Master Data
4) FA Master Data
5) Cost Centers
6) Profit Centers
Transaction Data:
Note that client wants to use only one offsetting conversion account instead of one account each for GL, AP, AR, FA etc
7) GL Balances
     what is the difference between balances and open items here and how do we post them (can i use f-02 for both) and document types?
     lets say i have GL 600100 which has a balance of $5000. If i want to post it during data conversion, should i post it as Dr 600100 Cr 700100 (this is a        offsetting account used only for conversion)
     how do you post an GL Open Items and what would be the accounting entries
8) Vendor Balances
     what is the difference between Vendor balances and Vendor Open items.
     lets say if i have 10 invoices pending payment for a vendor 10000, is the posting to KR doc type as Cr 10000 (vendor) Dr 700100 (this is a offsetting account used only for conversion) correct?
9) Customer Balances
     what is the difference between Customer balances and Customer Open items.
     lets say if i have 10 invoices pending payment by a customer 80000, is the posting to DR doc type as Dr 80000 (Customer) Cr 700100 (this is a offsetting account used only for conversion) correct?
10) Historical Data
     If the client asks us to post data from April 1 until May 31, what is the best approach, also here we are circumventing few things such as
     If there is a GR is done but not Invoiced, then these will be just posted as regular invoices (KR) instead of PO - GR - IV sequence
     If there is Invoice (PO based ones) but not paid, then these will be considered as regular open invoices (KR) as above
     like wise for O2C invoices too
I am trying to understand if i missing anything and if i have to follow any sequence. Appreciate if you guys can help with an example and if if i am missing any objects here...
Thanks
Shriya

Answer 1

Follow this and use LSMW.
LSMW for Functional Consultants in simple step-by-step way
Refer this to understand the basic:
Data Migration Part - Reg.
Regarding your questions: It does not matter whether you use single or five or six offsetting account. You should aware that at the end of the transfer your offsetting accounting balance should be zero.
You take trail balance (forget about the vendors / customers as you load them as open items)
All debit balances you debit in SAP and Credit the offsetting account. All credits you credit in SAP and debit offsetting account. Usually, GL open items would not be loaded, it is only balances. Open items are only for vendors and customers.
Note: You should NOT load tax line on the customer / vendor invoices, as they are already accounted for in the GL balances. Otherwise, your Migration account would never be zero.
For Assets, you need to load asset sub-ledger data separately through AS91 and GL balances separately. Use OAMK to set and reset the reconciliation accounts of assets. Once you loaded asset values, put them as reconciliation accounts and nobody should touch them.
You only load historical data line items of vendors or customers. You do  not post goods or invoices receipts again from MM. Mostly, what you can upload is open purchase orders.
Hope this helps.
Regards,
Ravi