Great info Paul thank you, we're using a MTL solution from a vendor
other than IBM, the configuration options you provided was not provided
to us, thus the configuration we choose
Carmen
On 10/13/2022 8:17 AM, Paul Gorlinsky wrote:
First of all, I am a manufacturer of a Virtual Tape Appliance that emulates
3480, 3490 and 3590 tapes, z/Appliance. We, like most VTAs that are not IBM's,
operate as a MTL ( manual tape library ), and we support auto mounting via the
LDD CCW ( Load Display ). For z/OS, that is the message like MABC001S that real
devices displayed. The M for mount, the S for SL label and then ABC001 for the
volume serial number. PRIVAT or SCRTCH for the vol ser indicate that the
appliance should pull from the scratch list it is maintaining.
Second, as part of the communication process, the LPAR number is sent. This
information along with the various CCWs that affect ASSIGNMENT, is how we
manage and communicate with the LPAR OS as to the availability of a DRIVE.
We support up to 254 LPARs, although that is beyond what IBM presently supports.
Now, you can VARY the device to be AUTOSWITCHed. That and configuring via the
IO/GEN multiple LPARs availability enables the use of a drive for several LPARs.
V 580,AS,ON
This is fine when you are operating a SYSPLEX, because a SYSPLEX typically
shares the tape pool/vault.
If that is not the case, then configure the VTA with multiple control units or
devices and limit the scope of the control unit or device to specific LPARs.
For example, with our z/Appliance you can configure a single control unit with
16 devices and each could be assigned a unique LPAR number and tape pool. Or
configure 16 Controllers with 4 devices each with each controller assigned to a
unique LPAR and yet they could all share the same pool if you wanted to do that.
The AUTOSWITCH configuration makes sense with expensive real devices. However,
with Virtual Tapes, we license by the number of active tape mounts, not the
number of devices defined. This avoids all the hand shaking that has to be done
by the OS to locate a free tape device. A process that adds latency to tape
drives in use.
If you have 4 LPARs and the maximum number of drives you would ever use is 8,
then define 4 control units with eight devices each and purchase a license for
8 devices. So even though you have 32 devices defined in the IOGEN, the license
would defer mounts greater than 8 in this case.
For additional information, please visit our website at
https://www.atsmigrations.com . Leave a contact and i would be happy to discuss
the process with you.
Thanks
Paul
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