Much of the information Eric referenced as part of this investigation came from things already written down, like the version numbers for the client software. That came from a manifest used by the configuration management system to push packages out. There was a copy of it (and where to find the current version) on the wiki. Not every organization will have all of those parts for every service, and some may have more. Large companies who have been running the same software for decades have tons of internal operations documents, occasionally long after the original vendor has given up.