Username change via external system?

[mypcb]

We've got vbulletin pretty much integrated into our existing member portal, but I have a quick question re: username changes. When you change an existing user's username via admincp, does it simply update the username field in the user table, or is there more to it?

We have a "change username" function built-in to our existing member portal and we want to update it so that when someone wants to change their username they can just do it there without having to also request that we manually change their vbulletin username ...

I know it's recommended to "update your counters" after changing a username (I assume this refers to the "Update Post Counts" function), which we can initiate programmatically, I'm just wondering if there's anything else we need to or should do besides simply updating the username in the user table?

I assume everything is handled internally based on the user's ID and the username is simply for show next to their posts, etc. so I'm hoping the username isn't found in any of the other 150+ tables that I'm not familiar with.