General Ledger Accounting - Reporting Financials (EhP3) - SAP Library
This above link will explain the details.
Please understand these below details.
1) data before EHP3 BI content GL account information should be stored in BSEG,BKPF tables. Similarly for Payable - BSIK,BSAK talbles and for Receivables stored in BSID,BSAD tables mostly.
In ECC side if new GL fucntionality implemented then most of the tables data will be stored for GL as FAGLFELXT (totals) and FAGLFLEXA for(Line items).
For these tables and new GL account fucntionality above link has the proper business content. These business content also have the datasources delta capabilities and direct access for the datasources to report on from ECC itself.
Further details will be explained clearly in the above link/.
Thanks
Sri