opening balances

hi experts

my project is going on live 1st of january

before going to this i have to maintain all the opening balances in sap system can you explain me how to maintain opening balances of sundry debtors,sundry creditors,bank and gl and also wanted to know is there any transaction code for doing this please explain in detail or if you have any document please forward

krishnagiri.gp@gmail.com

thanks

guru