Not sure why you want to do this. But if it is for high availability then you can do this: Set up two application servers which will connect to the same database (Primary - Acitve). But you can also create another database (Secondary) which will remain in passive mode.Use Database synchronization. Then use some cluster technology to shift the secondary database from passive to active mode if the primary database fails. This way you will achieve high availability of both application server as well as database.
This is the situation. We are going to implement another one help desk and want that they do not work with the data base in present production. We do not have another server to install new application server and another data base.
Would you consider using the folder feature to allow you to support separate "user" domains within the one service desk instance? I have done this a couple of times - it has the advantage of being able to use a common process to administer service management activity whilst maintaining separation/confidentiality.
There will of course need to be an admin who can "see" everything.