Dear Eduardo,
I like the part where you mention "memory leaks"...
All the mechanism described by Claudio is exactly a way of coping with the memory leaks present in web/application servers and offer anyhow to the end customers highly available systems. This is better described here:
http://www.spazioit.com/pages_en/sol_inf_en/distributed-sand-box-for-application-servers_en/
Ciao,
Maurizio