Creating a massive data file with each login

So it seems like WoW is creating a huge separate data file every time I log in and it is eating up my hard drive. When I go to the application folder and go under Data>data there is a separate “data.001,” “data.002,” etc. all of them between 900MB and 1.07GB. Can anyone tell me what’s causing this and how to fix it? Because I’ve been playing since vanilla and it’s never done this before.

The Data folder is where most of the game data is stored, it’s common data used by all versions of the game. I forget exactly when that started, but I think it was not long after they started doing classic servers.