(This post was published on the original RMS team blog in February 2010.)
If you plan to remove Active Directory Rights Management Services from your organization, you should first decommission the AD RMS cluster. This allows your AD RMS users to remove AD RMS protection from existing content. If you uninstall AD RMS without first decommissioning it, your protected content will no longer be accessible. Also, this process cannot be reversed. If you decommission a server, it cannot be restored to its previous AD RMS configuration. Here are a few links that can help you with this process:
It's hard to find good Information about this Topic for Server 2012. This article:
Is less specific, than this you are refferring to, but it also applies to 2012, even when the last Update is from 2007!