I found out that I am able to set user permissions using the ArcObjects commands grant or revoke with vb.net.
Ok,... but I have no idea how to create a user on the Oracle Database using VB.net and ArcObjects.
I don't want to use a direct Oracle connection using command "Create User...", I want to use the ArcSDE Connection with ArcObjects like "sdedatabaseCon.createUser("xy")" aso. Thats because I want to develop the application Oracle independent.
Thanks for all advice.
Jastro