Hi Matt,
Another quick response - I very appreciate your informations in this case - thanks for that 
Yes, I have the following constellation:
Active Directory -> SAP AS Java -> VIM Portal
And yes, the VIM-component is installed in my Standalone-SAP-AS-Java System.
The following procedure is requested from our customer:
The user (Domain-User, AD) should be able to logon to VIM-portal-URL.
So I want to know how should this work? Is it OK just to have the users in our AD or do we have to configure AS Java Identity Management to AD-Server?
Regards,
Manuel