Re: SPOOL/PAGE and cylinder zero
I remember IBM sent out an APAR for VM/SP to fix the problem. I would hope the code has been included in every VM since then. Bill Holder wrote: On Thu, 28 Aug 2008 01:54:51 -0400, Alan Altmark [EMAIL PROTECTED] wrote: ... Look in the archives of this listserver and you will find z/VM Developme nt stating that the volume label is safe from CP, even if cyl zero is allocated as page or spool. From a system management point of view, however, and for your sanity's sake, however, I suggest that cylinder zero SHOULD always be allocated a s PERM. Adding one additional cylinder will not help the system in any meaningful way and only serves to create controversy and risk. So, someone is wrong from a technology perspective, but right in terms of Best Practice. BTW, CP will happily hand out cylinder 0 to a guest if it is marked as T-disk. Dumb, perhaps, but true. Alan Altmark z/VM Development IBM Endicott = For what it's worth, ICKDSF (which CPFMTXA uses) was changed several year s ago and no longer permits allocation cylinder 0 as tdisk, though the prob lem could still occur with volumes formatted before that change (or by some other utility). Page and Spool usage of cylinder 0 has worked properly and been supported by the VM/XA - VM/ESA - z/VM lineage the entire time I've been with VM (th at is, since 1986). In that entire time, I'm unaware of even one problem involving page or spool usage of cylinder 0 (and I've been the team leade r / subsystem owner of the most affected area for 18+ of those years, so I wo uld have heard). Still, as long as there's any risk (with tdisk allocations) and confusion and misunderstanding, I won't argue with the recommended best practices of avoiding cylinder 0 simply to avoid having to have these discussions ever y few months (or at least, to keep them short). - Bill Holder, z/VM Development, IBM -- Stephen Frazier Information Technology Unit Oklahoma Department of Corrections 3400 Martin Luther King Oklahoma City, Ok, 73111-4298 Tel.: (405) 425-2549 Fax: (405) 425-2554 Pager: (405) 690-1828 email: stevef%doc.state.ok.us
Re: SPOOL/PAGE and cylinder zero
Historically, there was a problem, and that was a required restriction in those days. Modern CP does handle it correctly. You lose a trivial amount of disk space by skipping cyl 0 consistently (180K or so per volume). Even so, IMHO, it is still good practice to avoid cyl 0 for all packs as a matter of consistency. One less thing to document or to forget about and have something happen later (like DIRMAINT allocating a minidisk in an area where you *really* don't want it...sigh). From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, August 27, 2008 10:35 PM To: IBMVM@LISTSERV.UARK.EDU Subject: SPOOL/PAGE and cylinder zero I have always thought that CP handles properly SPOOL and PAGE areas starting on cylinder zero. It would be a shot on its own foot if CP would destroy the VOLID and the allocation map. However, someone is stating that SPOOL and PAGE MUST NOT be allocated on cylinder zero, I wonder if someone can positively answer this question and point to any documentation that may exist about this. Francisco A. S. Grossi
Re: SPOOL/PAGE and cylinder zero
On Thu, 28 Aug 2008 01:54:51 -0400, Alan Altmark [EMAIL PROTECTED] wrote: ... Look in the archives of this listserver and you will find z/VM Developme nt stating that the volume label is safe from CP, even if cyl zero is allocated as page or spool. From a system management point of view, however, and for your sanity's sake, however, I suggest that cylinder zero SHOULD always be allocated a s PERM. Adding one additional cylinder will not help the system in any meaningful way and only serves to create controversy and risk. So, someone is wrong from a technology perspective, but right in terms of Best Practice. BTW, CP will happily hand out cylinder 0 to a guest if it is marked as T-disk. Dumb, perhaps, but true. Alan Altmark z/VM Development IBM Endicott = For what it's worth, ICKDSF (which CPFMTXA uses) was changed several year s ago and no longer permits allocation cylinder 0 as tdisk, though the prob lem could still occur with volumes formatted before that change (or by some other utility). Page and Spool usage of cylinder 0 has worked properly and been supported by the VM/XA - VM/ESA - z/VM lineage the entire time I've been with VM (th at is, since 1986). In that entire time, I'm unaware of even one problem involving page or spool usage of cylinder 0 (and I've been the team leade r / subsystem owner of the most affected area for 18+ of those years, so I wo uld have heard). Still, as long as there's any risk (with tdisk allocations) and confusion and misunderstanding, I won't argue with the recommended best practices of avoiding cylinder 0 simply to avoid having to have these discussions ever y few months (or at least, to keep them short). - Bill Holder, z/VM Development, IBM
SPOOL/PAGE and cylinder zero
I have always thought that CP handles properly SPOOL and PAGE areas starting on cylinder zero. It would be a shot on its own foot if CP would destroy the VOLID and the allocation map. However, someone is stating that SPOOL and PAGE MUST NOT be allocated on cylinder zero, I wonder if someone can positively answer this question and point to any documentation that may exist about this. Francisco A. S. Grossi
Re: SPOOL/PAGE and cylinder zero
On Wednesday, 08/27/2008 at 10:34 EDT, [EMAIL PROTECTED] wrote: I have always thought that CP handles properly SPOOL and PAGE areas starting on cylinder zero. It would be a shot on its own foot if CP would destroy the VOLID and the allocation map. However, someone is stating that SPOOL and PAGE MUST NOT be allocated on cylinder zero, I wonder if someone can positively answer this question and point to any documentation that may exist about this. Look in the archives of this listserver and you will find z/VM Development stating that the volume label is safe from CP, even if cyl zero is allocated as page or spool. From a system management point of view, however, and for your sanity's sake, however, I suggest that cylinder zero SHOULD always be allocated as PERM. Adding one additional cylinder will not help the system in any meaningful way and only serves to create controversy and risk. So, someone is wrong from a technology perspective, but right in terms of Best Practice. BTW, CP will happily hand out cylinder 0 to a guest if it is marked as T-disk. Dumb, perhaps, but true. Alan Altmark z/VM Development IBM Endicott
