On Friday, 01/23/2009 at 07:58 EST, Clovis Pereira <[email protected]>
wrote:
> To avoid this risk doesn't put all these disks on SYSTEM CONFIG.
> If you need repeated volsers, is secure to use fullpack dasd defined as
> MDISK ... DEVNO. VM mounts them only when necessary and volser doesn't
> matter
> I know a VM system that process many Disaster Recovery tests
> simultaneously, where many customers keep your dasds as 530RES by
example.
> Use of DEVNO keep all secure and independent. Of course, the owned dasds
> have another different volsers and was mounted at lowest addresses.
> MVS doesn't work this way, so these dasds must be defined as OFFLINE to
> other MVS LPARs.
Commandments 11 and 12 still apply. DEVNO will not protect you as it is
simply a way to give a guest a full-pack minidisk without regard to the
volser. If the guest changes the volser to match a volser that is listed
in SYSTEM CONFIG, then you are at risk on the next IPL.
Do not depend on the lowest-address-wins algorithm. That was a way to
ensure a determinate result at IPL, not a way to protect the system from
duplicate volsers. What would happen if one of your low-address volumes
is offline for some reason? Answer: CP will pick the next one. And if
the system comes up, it may well overwrite user data on the volume.
Iffen I had my druthers, I'druther SYSTEM CONFIG allowed volumes to be
specified by device address instead of, or in addition to, volser. ("Odd,
my checkpoint area doesn't have the same volser today.")
Alan Altmark
z/VM Development
IBM Endicott
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