Currently, in the Virtual DataPort, an administrator user would create, modify and delete **any** databases without any restrictions.
For your scenario, I would ask an administrator user to create databases A and B and assign the Julien user( Normal user) with administrator privilege over these databases. Also I will ensure that he is not provided with any other privilege like connect, create, metadata to access database C created by another user.
In order to automate the creation of virtual database, user, roles and assignment of privilege, I would follow the below steps:
* Launch Scheduler Administration tool and create a vdp job.
* Provide the VQL scripts in Extraction section to [Create Databases, Users, Roles and Access Privileges](https://community.denodo.com/docs/html/browse/8.0/en/vdp/vql/creating_databases_users_roles_and_access_privileges/creating_databases_users_roles_and_access_privileges#creating-databases-users-roles-and-access-privileges).
* Schedule the job execution time in the trigger section.
You could refer to the Knowledge base article for [Creating a Denodo Scheduler Job](https://community.denodo.com/kb/en/view/document/Creating%20a%20Denodo%20Scheduler%20Job) for more information.
Hope this helps