>Do people really have Linux systems that run 7 x 24? Yes, silly people want to withdraw money (legit or illegit) at any hour of the day or night from an ATM.
But Jim should have just bought another z10 and put those with continuous availability (a.k.a. 24x7x365) requirements on duplicate servers on different boxes rather than having IBM add him a feachur ;). Kidding, Jim - dynamic memory is a *good thing* especially if z/OS can do it too :) WebSphere clustering, DB2 HADR, Oracle Data Guard... All those things and more make it possible. Planned outages happen here nearly every weekend (not that that is desirable either :) Marcy "This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation." -----Original Message----- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Alan Ackerman Sent: Tuesday, August 05, 2008 11:06 PM To: [email protected] Subject: Re: [IBMVM] ADD VIRTUAL MEMORY DYNAMICALLY 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
