[OGWhales]

Not personally, but most every migration attempt I have heard about has gone similarly.

We run a mainframe shop and for us the cost is fairly reasonable, and the high bandwidth/reliability (even with the cpu pinned to 100%) is the most critical aspect to us. Ignoring the risk and cost of migration, I am not even sure that an alternative would be cheaper... but it is quite difficult to determine the cost and my boss obviously factors in the cost/risk of migration anytime this comes up.

I'd be curios to hear of any successful total migration attempts. Most shops I know of keep their mainframe and build around it with modern tools and we do as well.

[treesknees]

That's been the experience I've had as well. One company I worked for around 2015 had 5 or 6 mainframes (which they kept upgraded to the latest hardware on an IBM lease program every few years), and it was well understood that the number of distributed computing servers required to keep up with the volume and resiliency of the mainframe would be too great to even consider.

Another company I interviewed with did just what you said, they built REST APIs and other "modern" interfaces to the mainframes so that 99% of app developers in the company don't have to learn anything about the mainframe.