logout and clear session

[Slawek]

hi
problem: user cliks on menu with action logout...
how to clear all memory associated with his session (for ex. large beans)?
i can get session in action method:
	FacesContext facesContext = FacesContext.getCurrentInstance();
	SessionMap session = 
(SessionMap)facesContext.getExternalContext().getSessionMap();
	//session=null; - that doesnt clear session:/

and what should i do to clear memory (set null references to tell garbage 
collector to whipe out objects without waiting when session expires)?

thanks for your time Men!
Slawek