Reload historical data

Hi,

We are looking to reload 7 years of historical data to ODS1 from R/3 purchasing extractor, can you please advise the best approach or steps for this with out breaking the delta and ease cumbersome reload. Cannot do load from PSA since data is wrong.  Data also flows to ODS2 from ODS1.  I only heard there is also update statement for the reload if updating or reloading ONLY some fields which contains incorrect data.  I do not know how to write sql statement for the reload.  Any insights will be helpful.

Thanks

Di