Here is a paper on that topic: http://pmg.csail.mit.edu/~ajmani/papers/ecoop06-upgrades.pdf http://pmg.csail.mit.edu/~ajmani/papers/ecoop06-upgrades.pdf Their

Here is a paper on that topic: http://pmg.csail.mit.edu/~ajmani/papers/ecoop06-upgrades.pdf http://pmg.csail.mit.edu/~ajmani/papers/ecoop06-upgrades.pdf Their examples show that it is not possible to do all application upgrades without downtime, and they show how to keep downtime to a minimum (e.g. by only making parts of your application inaccessible).