Denormalized usernames

[CyberAP]

There is a new option in preferences called 'Update denormalized usernames on username change'.
I hardly can understand what does this option do. The description says:

When you change a user's username, you may instruct the system to update all denormalized versions of that username. This can be an intensive operation, and if you have very large amounts of data you may wish to disable it.

That's confusing for me. What the denormalized username is and what will change if I disable that option?
This is mostly needed for a russian translation.

 

[Mike]

It controls whether we go searching in a lot of tables for the old user name and update it to the new user name. (That's a really simplified, and thus possibly misleading description.)

Note this doesn't refer to quoted posts.

 

[ragtek]

lol
perfect timing
http://xenforo.com/community/posts/214982/
hope this helps^^