Alan, You can rely on MVCL to operate the way the POP says it will. My impression from reading the POP is that the MVCL is an interruptible instruction so if you're coding first level on a multi processor configuration without an operating system to manager things for you the results of the MVCL can be erractic in appearance even if the instruction has done exactly what it was supposed to since another thread on another processor was updating the storage the MVCL was operating on.
Paul Paul, your wording suggests that MVCL isn't reliable under some conditions. The word "reliable" in this context must mean "conformance to specification". I.e. you are saying that sometimes MVCL doesn't do what the book says it does. Details, please. (Or I've misunderstood what you were trying to say!) Alan Altmark Sr. Software Engineer IBM z/VM Development
