SAP EP 7.4 user licences

I am having ecc user licences say 100 And portal user licences say 600.

ECC users having access of ECC system and not portal.

And portal users have only access of portal and not ECC.

so my question is suppose user login in EP and make some changes in ess mss on ep then how it going to store in ECC.

Because at the end data is comming from ECC and store in ECC only and not of EP.

OR there is any other way to deal with this situation.