If you have staff who will be leaving your department you need to consider all of the services that staff member may have used. They may well be owners of shared files, of automated scripts, they might be the manager of a mail-list, and they might own a vital shared mailbox.
There are so many things to consider that IT Services have compiled a list that you can check (requires SSO to view) – and you should begin planning at least a month before the staff member’s last day. Trying to reinstate or recover content afterwards is not straightforward and, in many cases, can’t be done.
Here’s the link: https://help.it.ox.ac.uk/removing-access-for-staff