Since OS/400 aka IBM i has a built in database and is often used for inventory and payroll management, one could write a program for it that enables it to effectively manage a large lighting collection.

Obviously these days there are much better solutions, but this is more interesting because it uses very cool old hardware and a somewhat obscure operating system.

More information on OS/400 at Wikipedia site: https://en.wikipedia.org/wiki/IBM_i

So long as you can back up the data to access from a modern system (including being able to open the file formats), if the old hardware fails...

I am not familiar with this system, but as long as there is networking or a serial port you can probably do quite unlimited stuff with it, at least as a terminal to another system

I believe it has TCP/IP, and it definitely has a serial port for IBM’s special terminals (or a PC running IBM ACS)
They also often have a tape drive for backups, CD/DVD drive, and hot swappable HDDs in bays

Though I would probably run this application on pub400, a free public server running the latest version of IBM i so that I wouldn’t have to worry about stuff like that, even though I have an IBM POWER system that I could use, but it will be running Linux.