When you delete a user:
You can reuse a username after it has been deleted.
Warning: The action of deleting a user cannot be undone. After you delete a user, you cannot undelete that user.
An Administrator can delete other Administrators but cannot delete a System Administrator. A System Administrator can delete users of any role.
Note: If two different administrators try to delete the same user at the same time, only the first deletion succeeds and appears in User Audit reports. The second user receives an error on the attempt to delete.
To delete users:
Note: The System Administrator cannot be deleted.