I have written two new Knowledge documents providing start-to-finish examples of how to restrict access to the CV when using Visual DBA, and these are now available on the Support Online site. The documents are:
You should be able to click on the embedded links in the descriptions above to find these easily. They describe ways to use the Visual DBA Enhanced Object Security feature to allow either read-only access to a CV; or to restrict a user's access to specific entities within the CV.
I hope these are helpful! If it would be helpful to have additional profile examples or Knowledge Documents about how to limit access through Visual DBA, let me know and I will work on creating them.