Q: OS/2 does not support on the fly resolution change
Alex Taylor: Because it's a fundamental design limitation of Presentation Manager. The only ones who could fix it are IBM, and they made it obvious years ago that they're not interested in doing so. Thus, we are indeed stuck with it.
I don't remember the real details! But some of the DLL's loaded by OS/2 for PMSHELL need to unloaded for the system to switch resolution. The problem is that can not be done. I don't know if all DLL's are loaded in such a fashion on OS/2 or if its just a subset of DLL's. But because these DLL's can not be unloaded (reset pmshell.exe ?) the resolution can not be switched without a reboot of the system.