JBA ML - Sales Analysis update

Hello everyone,
,
     we have a particular situation whereby we are implementing the
distribution & financials applications of system 21 for 1 particular
company. There is a backlog of 3 months invoices being input in SOP .
Would anyone know
1) how does the system determine to which period in Sales Analysis the SOP
transactions are being summarised to?
(on one side, in SOP,  we  have a) document date b) invoice date) c)
inventory period  and on the other side in SA we have a calendar)
2) We have already run a sales history update for that company and the
period updated is now what we expected. We would therefore like to delete
the SA records and re-run the update.
The questions therefore are:
a)Is SAP20 the only file in SS from which records for that company is to be
deleted?
b) Which flag in which SOP files (OEP65?, OEP70?) must be reset so that a
SA history update re-run will process these records again?

Note: on our system, there are many other companies which have been setup,
which are already on-line and are also happily using the Sales Analysis
application


Regards