Gerhard,

I am not sure if this is what you are looking for, but a bit of reading on Garbage collection in Mendix 7 might be worthwhile, as garbage collection has moved to the client (browser).  Documentation can be found here: https://docs.mendix.com/refguide/transient-objects-garbage-collecting

If you asked this question for security reasons, this change in behavior could have significant security implications (i.e. for apps in regulated industries like finance and healthcare, it seems to me that security considerations on the client side require quite a bit of analysis and work to ensure that these applications meet compliance requirements).

From the documentation linked above, transient objects are discarded as soon as they are no longer in use and no associated objects are in use.  The only exception to this is transient objects that are associated to the current user or current session.  These objects will persist unless specifically deleted.  

Hope that helps,

Mike