This is something I've heard a lot throughout my career, from practically every mainframe operator/admin I've ever worked with, and up until now, I never really questioned it, or had a reason to care one way or another. Never reboot a mainframe, because that's particularly awful heresy, and it creates all kinds of risks and problems, plus IBM kills a puppy every time someone reboots a mainframe. (Or something along those lines, anyway.)
Well, recently, I've been forced into a situation where I have a reason to care, and the more I think about it, the less sense it makes. Mainframe hardware is designed to be resilient, the OS on those things is about as stable as you can get, and I'm pretty sure IBM doesn't actually have a large stockpile of puppies to murder every time an iSeries gets rebooted.
Of course, I get that server reboots in general are poor practice, or an option of last resort, or something you should only do when the on-call guy has a hot date lined up, but I'm currently jumping through all kinds of crazy hoops to avoid having to reboot an iSeries because... well, "just because," it seems.
With that in mind, can anyone with mainframe experience explain the technical reason(s) that rebooting a mainframe is especially bad compared to rebooting a *nix or Windows server?