Scream-tracing
A little over a decade ago I was contracting with a large software supplier/bodyshop[0] that was closing down one of their branch offices. Which involved moving most of the systems in that office (let's call it 'E') to the one where I was orking (let's call it 'N'). After some culling and rearranging about 53 racks had to be moved from E to N, but initially N had only space for 18. So we had a look around to see what could be culled from N. This promised to be quite worthwhile, because the floor was littered with gear for customer projects that had long been delivered, patched, upgraded, patched some more and declared finished. With the project teams long disbanded, reassigned to other projects, split off into separate ventures and members having left the company or even this earthly plane. Documentation was either stored in a filing cabinet in a disused lavatory, or buried in soft peat for three months and recycled as firelighters. So I called a meeting of all department heads that might have some equipment in use on the floor in N, handed them a document template and a pile of stick-on envelopes[1], and the notice that any system not labeled two weeks from that date would be subject to gravitationally motivated impact tests in the car park.
Of course we did not do so right away after those two weeks, instead simply unplugging any network cabling[2] from those systems. And one sub-department came and wailed bitterly that they could not access their test rig, explaining that their lack of labeling was because of the department they were part of not passing on the meeting request. We then reconnected their gear, and there was much rejoicing.
(this action netted twelve racks of orphan systems that nevertheless had been running, consuming power and cooling, for several years)
[0] they clearly had insufficient bodies available with the skills required for their own operations.
[1] none of this faffing about with a shared database, which would have taken weeks to set up, deploy, get everyone to add their data (for which they probably would have needed to visit the computer room floor), after which we would have needed to match that data with the systems ourselves anyway.
[2] deemed safer than powering off; quite a few systems were expected to suffer Spontaneous Loss of Magic Smoke in case they needed to be powered back on.