There's some disagreement on the cabinet release being a factor for new software not booting up on old cabinets. The last thing I want to do is mislead anyone, so I'll detail what I mean by "the hard way".
On at least 3 separate occasions, I've upgraded CICS's I had installed when the CICS had first come out. They were running fine on 1.0, and 2.0 software, and were even ok up to 4.1. When I tried to bring them up to 6.1, or newer, they would not come up. When I moved them back to their original software, they came up clean, and replacing the cabinet, the new software came up fine.
The only common point I've found was that all these cabinets were rel 1, and the new cabinets were rel 2. This was confirmed by the tech support I used when I had trouble the first time. Ever since, I check the cabinet before I propose an upgrade.
Oh, yeah... If I recall, the cabinet release is on a label between the Amps, above the power cord.