On Tue, 5 Aug 2008 09:58:58 -0700, Schuh, Richard <[EMAIL PROTECTED]> wrote :
>Yes, it can add, but not subtract without LPAR deactivation. Let me know >when the ability to dynamically remove previously added storage is >available, and I will be more enthusiastic. > >Regards, >Richard Schuh Deleting memory is a lot harder. What if there are control blocks in there? You could use handles (pointer s to pointers) but that is a complete rewrite. If a control block can move, you cannot trust a registe r to continue to point to it. I think this would require a new instruction set to do the pointer to pointer resolution directly. Or you can fence off areas and say "no control blocks allowed in here". T hat would increase the complexity of operating systems, though. Such storage could only be used to back up guest or pageable operating system pages. If you wanted to remove a block of memory, you would have to initiate a m ass page-out to clear the area. I'd rather not have to resolve the performance issues that migh t occur. Does z/OS do this? I don't think the ability to remove memory is something I want IBM to spe nd scarce z/VM development dollars on. Another thought: The need to add memory may be an emergency situation. The need to remove it again is not an emergency and can be planned. How important avoiding an IML may be depend s on whether you really want to achieve 7 x 24 operation. 7 x 24 operation is going to cos t you something -- including adequate capacity and memory. There are other ways to achieve 7 x 24 operation. We don't run any system s with true 7 x 24 requirements. We may run pairs of systems, or sysplexes of systems, but n ot single systems. Do people really have Linux systems that run 7 x 24? Alan Ackerman Alan (dot) Ackerman (at) Bank of America (dot) com
