user management for ICH and Portal

Hi,

how is the user management be done when having users accessing ICH data through the SAP Portal?

E.g. a user should be able to see inventory overview through the portal. Do the portal and ICH necessarily have their user repositories or is it possible to share the same user repository for both? If sharing is possible, how can the different roles for the portal and for the ICH be handled? If it is only possible with two separate repositories, can the replication mechanism of the UME be used (like in the portal and SRM scenario)?

Thanks a lot for your help. If anybody has got a document explaining the user management of ICH, it would help me a lot to receive it.

Best regards,

Markus