If you do not need the data delete with a cron job from also database
You can also anonymize user data if you want to use for statistical purpose.
OK, how exactly to delete users from the database? I'm desperately trying to find a way to do that. Deleting user's record from the mdl_user DB table is not an option because it would break relations with other tables.
Is there any easy way to anonymize old deleted users without having to do it manually in the database by executing a DB query?