I was under a spam attack with over 100K fake users, had to disable registration, in the process of deleting all users as per Sebastian Leupold blog article:
Deleted all users folders manually, from the server via remote desktop access.
I then went to the File Manager/Admin to perform a sync to get rid of all folder entries and folder permissions in the database.
With over 100K user folders, it is taking sometime, with 12 hours now and I am half way thought, while with little impact on site performance
Have noticed the folders reference is being removed without an issue (table: "folders") but the corresponding folder permissions (in table: folderpermisssions) are NOT REMOVED!
With an average of 5 rows in the permissions table per folder, I'm having over 500,000 Orphan rows in the folderpemissions table .
I am using DNN 7.3.4, SQL 2012 web edition on a Win 2102 standard edition.