At the moment we don't have decommissioned hosts that are still racked clearly marked as decommissioned. Hence one has always the doubt that the host is actually still in service, despite not finding it in site.pp on puppet.

I think we should have a clear and easy to spot way to mark decommissioned hosts on racktables, see https://racktables.wikimedia.org/index.php?page=object&tab=default&object_id=1769 for example.