Discussion:
I have to use the 'O' word.
(too old to reply)
Steve Gentry
2006-02-08 13:21:34 UTC
Permalink
Hello. We are a VM shop only, therefore our DASD is formatted for VM and
have a VM VTOC. Is it possible to put an osvtoc (the 'O' word <g>) on
these volumes without totally reformatting the drive, etc?
Thanks,
Steve G.
David Boyes
2006-02-08 15:36:08 UTC
Permalink
They already have one (DSF CPVOL FORMAT puts an OS VTOC on VM volumes
that indicates that the volume is full wrt to OS allocation).


________________________________

From: VM/ESA and z/VM Discussions
[mailto:VMESA-***@LISTSERV.UARK.EDU] On Behalf Of Steve Gentry
Sent: Wednesday, February 08, 2006 8:30 AM
To: VMESA-***@LISTSERV.UARK.EDU
Subject: I have to use the 'O' word.



Hello. We are a VM shop only, therefore our DASD is formatted
for VM and have a VM VTOC. Is it possible to put an osvtoc (the 'O'
word <g>) on these volumes without totally reformatting the drive, etc?
Thanks,
Steve G.
Schuh, Richard
2006-02-08 16:35:12 UTC
Permalink
And the way that a full volume is indicated was only partially correct in the good old days. I don't know about the modern VTOCs, they may be handled much differently.

The way a volume was marked as full was to write a Format 5 DSCB indicating no free space. To complete the process, there should also have been a Format 1 DSCB describing an extent encompassing all the tracks except for the VTOC extent. There was, maybe still is, a very dangerous bit in the Format 4 DSCB that indicates either a DOS or a Damaged VTOC (DOS came first, using it for a Damaged VTOC came later. I guess in the eyes of the OS, including OS/360, VS1, SVS, and at least the early MVSes, developers, there was no difference.). Whenever the allocation routines tried to allocate space on the volume, the bit would be turned on and then turned off when allocation was finished with the volume. If this bit was on when OS tried to allocate space on the disk, the allocation routines would reconstruct the F5 DSCB chain by creating an F5 that has all space free and then sequentially read the VTOC, removing allocated extents one-by-one from this dummy F5. It would then write a chain of F5s that included all non-allocated space. For a VTOC that only had an F5 indicating no free space and no other DSCB that allocated the entire volume, the new F5 would include the entire volume except for the label track and the VTOC extent. Recovery from this was very painful, both to OS and VM.


Regards,
Richard Schuh

-----Original Message-----
From: VM/ESA and z/VM Discussions [mailto:VMESA-***@LISTSERV.UARK.EDU]On Behalf Of David Boyes
Sent: Wednesday, February 08, 2006 7:36 AM
To: VMESA-***@LISTSERV.UARK.EDU
Subject: Re: I have to use the 'O' word.

They already have one (DSF CPVOL FORMAT puts an OS VTOC on VM volumes that indicates that the volume is full wrt to OS allocation).

_____

From: VM/ESA and z/VM Discussions [mailto:VMESA-***@LISTSERV.UARK.EDU] On Behalf Of Steve Gentry
Sent: Wednesday, February 08, 2006 8:30 AM
To: VMESA-***@LISTSERV.UARK.EDU
Subject: I have to use the 'O' word.

Hello. We are a VM shop only, therefore our DASD is formatted for VM and have a VM VTOC. Is it possible to put an osvtoc (the 'O' word <g>) on these volumes without totally reformatting the drive, etc?
Thanks,
Steve G.
Rick Troth
2006-02-08 23:31:07 UTC
Permalink
...
> I presume that you have a reason to have an OS VTOC. It is not necessary
> to have an OS VTOC to be able to make VM volumes available on a z/OS
> system. z/OS can mount a VM volume and leaving the standard VM volume
> labels will prevent z/OS from writing over you VM mini-disks because the
> volume will appear to have no free space. If you want an OS-formatted disk
> to run a guest, ...

Right. CP vols. But z/OS doesn't like CMS formatted volumes.
While CP is happy with full-volume CMS content, last I heard
z/OS still got heartburn over it. I would be glad to hear
a report that this is no longer true.

-- R;
Jim Bohnsack
2006-02-09 03:16:48 UTC
Permalink
Why would anyone want to use CMS formatted volumes? That suggests that
someone is going to have an mdisk that starts on real cyl 0 and allows the
owner of the mdisk (volume) to change the real vol serial. There is simply
no reason at all to allow that. Even if you say that real cyl 0 is going
to be an mdisk owned by a $ALLOC$ type of userid, why would you want to
format it using CMS. CP and MVS are real operating systems. Give them
real operating system labels and VTOCs.

Jim

At 06:31 PM 2/8/2006, you wrote:
> ...
> > I presume that you have a reason to have an OS VTOC. It is not necessary
> > to have an OS VTOC to be able to make VM volumes available on a z/OS
> > system. z/OS can mount a VM volume and leaving the standard VM volume
> > labels will prevent z/OS from writing over you VM mini-disks because the
> > volume will appear to have no free space. If you want an OS-formatted disk
> > to run a guest, ...
>
>Right. CP vols. But z/OS doesn't like CMS formatted volumes.
>While CP is happy with full-volume CMS content, last I heard
>z/OS still got heartburn over it. I would be glad to hear
>a report that this is no longer true.
>
>-- R;

Jim Bohnsack
Cornell Univ.
(607) 255-1760
Jeff Gribbin, EDS
2006-02-09 07:26:16 UTC
Permalink
Hello Stephen,
Hopefully by now you've got the idea that the, "How" of an OS VTOC is
quite straightforward - but have we really answered your question /
resolved your problem? I'm not sure. I think it'd help us if you could
give a bit more background on what exactly you're trying to achieve - if
it's as simple a just getting a VM volume online to zOS for (say) taking
full-volume backups then you probably now have all you need ... but I've
got a sneaking feeling that you're looking for something more.

Can you share some of the, "why" (you want an OS VTOC) with us? That way -
if we haven't done so already - we might be able to help resolve whatever
your, "real problem" might be.

Regards
Jeff Gribbin

(P.S. Joking aside, never feel the need to have to apologise when you
acknowledge zOS' existence on this list - most folk here actually have a
deep respect for its power and capabilities - "He Aint Heavy - He's My
Brother".)
Jim Bohnsack
2006-02-09 13:29:15 UTC
Permalink
Steve--The CP owned volumes, assuming they have CP allocated space on them
such as DRCT, PAGE, TDSK, or SPOOL already have a "osvtoc" on them. If you
enter, from a priviliged id such as MAINT, Q ALLOC, you will see a display
of those volumes. Those you can be sure of as having a useable
VTOC. Another way to tell if there is an "osvtoc" and not a volume label
that would have been created by the CMS FORMAT program is to use ICKDSF
CPVOL LIST on the volume. The CP owned volumes I mentioned above would
have been formatted with CPFMTXA or ICKDSF with the CPVOL option (same
thing). That is what you want. CPVOL will leave a format 6 (or is it 5)
DSCB on the volume showing that the volume is completely full and it will
also create a "osvtoc". So, if you see the following when you use ICKDSF
with CPVOL LIST you're ok, assuming that the number of cylinders shown is
the same as the size of your volumes rather than the 1 cyl tdisk I used
here for the example.

cpvol unit(111) nvfy list
CPVOL UNIT(111) NVFY LIST
ICK00700I DEVICE INFORMATION FOR 0111 IS CURRENTLY AS FOLLOWS:
PHYSICAL DEVICE = 3390
STORAGE CONTROLLER = 3990
STORAGE CONTROL DESCRIPTOR = E9
DEVICE DESCRIPTOR = 0A
ADDITIONAL DEVICE INFORMATION = 48001B35
ICK04000I DEVICE IS IN SIMPLEX STATE
ICK00703I DEVICE IS OPERATED AS A MINIDISK
ICK00091I 0111 NED=002105.000.IBM.13.000000023792
ICK091I 0111 NED=002105.000.IBM.13.000000023792
ICK03090I VOLUME SERIAL = 111111
ICK03024I DEVICE IS CURRENTLY FORMATTED WITHOUT FILLER RECORDS
ICK03000I CPVOL REPORT FOR 0111 FOLLOWS:

ICK03021I 0111 IS FORMATTED FOR VM/XA|ESA MODE

CYLINDER ALLOCATION CURRENTLY IS AS FOLLOWS:
TYPE START END TOTAL
---- ----- --- -----
PERM 0 0 1

ICK00001I FUNCTION COMPLETED, HIGHEST CONDITION CODE WAS 0


At 07:57 AM 2/9/2006, you wrote:

>Thanks all for the comments. I cannot go into extreme detail on this due
>to confidentiality issues. But, let's say I'm a zOS shop with no VM
>experience. I suddenly have access to VM machine and I want to do full
>volume backups because that's all I know how to do in zOS. Will putting
>an osvtoc on my VM 'sysres' volumes cause problems? The answer I've
>gleaned is 'yes' if it is the cp volumes i.e., 520RES, 520W01, etc. We
>do full volume backups on 7 'system' drives. All other backups are taken
>care of by using a 3rd party product, which is to say we don't do full
>volume back ups on these.
>I have nothing personal against zOS. EVERY operating system has it's
>strengths and weaknesses. It's when factions put blinders on and only see
>their o/s as an end all is when I get a little passionate about operating
>systems.
>Thanks again to all that have responded.
>Steve G.
>
>
>
>"Jeff Gribbin, EDS" <***@EDS.COM>
>Sent by: VM/ESA and z/VM Discussions <VMESA-***@LISTSERV.UARK.EDU>
>
>02/09/2006 02:26 AM
>Please respond to VM/ESA and z/VM Discussions
>
> To: VMESA-***@LISTSERV.UARK.EDU
> cc:
> Subject: Re: I have to use the 'O' word.
>
>
>Hello Stephen,
>Hopefully by now you've got the idea that the, "How" of an OS VTOC is
>quite straightforward - but have we really answered your question /
>resolved your problem? I'm not sure. I think it'd help us if you could
>
>give a bit more background on what exactly you're trying to achieve - if
>
>it's as simple a just getting a VM volume online to zOS for (say) taking
>
>full-volume backups then you probably now have all you need ... but I've
>
>got a sneaking feeling that you're looking for something more.
>
>Can you share some of the, "why" (you want an OS VTOC) with us? That way
>-
>if we haven't done so already - we might be able to help resolve whatever
>
>your, "real problem" might be.
>
>Regards
>Jeff Gribbin
>
>(P.S. Joking aside, never feel the need to have to apologise when you
>acknowledge zOS' existence on this list - most folk here actually have a
>
>deep respect for its power and capabilities - "He Aint Heavy - He's My
>
>Brother".)
>

Jim Bohnsack
Cornell Univ.
(607) 255-1760
Schuh, Richard
2006-02-09 16:33:44 UTC
Permalink
If the owner changes the real volser, he/she will not be able to link to the disk a second time :)

Regards,
Richard Schuh

-----Original Message-----
From: VM/ESA and z/VM Discussions [mailto:VMESA-***@LISTSERV.UARK.EDU] On Behalf Of Jim Bohnsack
Sent: Wednesday, February 08, 2006 7:17 PM
To: VMESA-***@LISTSERV.UARK.EDU
Subject: Re: I have to use the 'O' word.

Why would anyone want to use CMS formatted volumes? That suggests that
someone is going to have an mdisk that starts on real cyl 0 and allows the
owner of the mdisk (volume) to change the real vol serial. There is simply
no reason at all to allow that. Even if you say that real cyl 0 is going
to be an mdisk owned by a $ALLOC$ type of userid, why would you want to
format it using CMS. CP and MVS are real operating systems. Give them
real operating system labels and VTOCs.

Jim

At 06:31 PM 2/8/2006, you wrote:
> ...
> > I presume that you have a reason to have an OS VTOC. It is not necessary
> > to have an OS VTOC to be able to make VM volumes available on a z/OS
> > system. z/OS can mount a VM volume and leaving the standard VM volume
> > labels will prevent z/OS from writing over you VM mini-disks because the
> > volume will appear to have no free space. If you want an OS-formatted disk
> > to run a guest, ...
>
>Right. CP vols. But z/OS doesn't like CMS formatted volumes.
>While CP is happy with full-volume CMS content, last I heard
>z/OS still got heartburn over it. I would be glad to hear
>a report that this is no longer true.
>
>-- R;

Jim Bohnsack
Cornell Univ.
(607) 255-1760
Nix, Robert P.
2006-02-13 21:55:14 UTC
Permalink
The first question that comes to mind would be "Why"?

The VM label has a perfectly fine OS VTOC in it, showing that the drive is full. Since you can't mix zOS data and zVM minidisks on the same volume (other than when you're running zOS as a guest and give him his own minidisk there), there should be no need to put a different VTOC on the drive to have it seen by zOS.

To that end, I label drives all the time that come online to our zOS system, and they've never had a problem with them, and I've never had a problem with them using my drives by accident either.

--
Robert P. Nix Mayo Foundation
RO-OC-1-13 200 First Street SW
507-284-0844 Rochester, MN 55905
-----
"In theory, theory and practice are the same, but
in practice, theory and practice are different."



_____

From: VM/ESA and z/VM Discussions [mailto:VMESA-***@LISTSERV.UARK.EDU] On Behalf Of Steve Gentry
Sent: Wednesday, February 08, 2006 7:22 AM
To: VMESA-***@LISTSERV.UARK.EDU
Subject: I have to use the 'O' word.



Hello. We are a VM shop only, therefore our DASD is formatted for VM and have a VM VTOC. Is it possible to put an osvtoc (the 'O' word <g>) on these volumes without totally reformatting the drive, etc?
Thanks,
Steve G.
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