If you are in a site collection’s top level site, which I assume /departments/itdept is in your example, go to site settings and you do not see a Site Collection Administration column at all it means you are not a site collection admin. If you
see the column and are not seeing the SLAM Control Panel link it is because you need to activate the SLAM feature in site collection features. I point this out because the SLAM Control Panel executes everything with the assumption that the admin is a
site collection admin. By simply navigating to it by address may lead to other unexpected errors.
As for setting up the slam config for the itdept site collection you should add another DataMapping element to your slam.config.
So you have your top level one like:
With whatever the DataSchema is, then you add another one at the same level like:
<DataMapping SiteCollection="departments/itdept" DataSchema="dbo">
This DataMapping, as I have given, will use the same connection string as the root site collection. You could alternatively add another connection string to the ConnectionStrings section and add ConnectionString=”…” to the DataMapping
element in case you wanted it to slam to a different database.
In any case, once you have the DataMapping section for the itdept site collection doing validation in the SLAM Control Panel under that site collection will only refer to lists and content types defined in that DataMapping.