What is the purpose of BAPI_TRANSACTION_COMMIT?

-BAPI_TRANSACTION_COMMIT is used when you want to update data into database table.
-Before updating into database table the data to be updated is stored in the UPDATE LOG.
-When the system invokes this Functiona module or 'Commit Work' statement then the database table is updated with the data stored in update log.

-Each BAPI Function Module has its own COMMIT WORK. This is stateless and it is good in some situations.You could not combine multiple update BAPIs into a single LUW( Logical Unit of Work ). In some applications you need to have more controle on LUW's. Hence, SAP R/3 4.0 onwords SAP changed its feature that all updates should be in stateful and allow the client programmer that BAPI_TRANSACTION_COMMIT to be called whenever he is needed.