Virtual Tape support on z/VSE comes in two flavors, VSAM and remote.
You can direct a virtual tape file to either.
If you redirect it to a VSAM file, it can be very fast and a very good
way to replace intermediate tape handling within a job stream or for
backups. As long as there is enough VSAM space available to handle the
output data.
If you redirect the file to a remote system, that remote system runs a
java application that handles all of the communication and data storage.
This java application can run on (almost) anything (even z/OS, I
guess, so a zAAP could be used). The mainframe (z/VSE) decides the file
name that is stored on the remote server (through the VSE equivalent of
the DD statement).
The remote method uses TCP/IP communications and is very well suited to
Linux on System z over Hipersockets for it's speed.
Virtual Tape support is fairly well integrated into tape handling on
VSE. A special JCL statement was created for the initiation and
termination of VTAPE handling, which starts a special job (think started
task, I guess) that does the communication to the VSAM file or remote
system through a shared buffer area.
I've suggested that z/VM adopt this approach so that virtual tapes from
z/VSE and z/VM can live in the same place. There's probably no reason
that z/OS can not do the same.
McKown, John wrote:
-----Original Message-----
From: IBM Mainframe Discussion List
[mailto:[EMAIL PROTECTED] On Behalf Of Knutson, Sam
Sent: Monday, November 19, 2007 7:13 AM
To: [email protected]
Subject: Re: Transferring data from a different site that uses VTS
Hi,
If IBM would add support into z/OS for mounting a sequential
file in AWS
format on a virtual tape drive it would solve a many of these data
exchange problems.
z/VSE seems to be ahead of the game here.
This would also significantly simplify the electronic delivery of
software by OEMs who are still using tape images with a
required step to
reconstitute them into a physical tape before proceeding with the
install.
Best Regards,
Sam Knutson, GEICO
Well, I will put in a "plug" for FlexCUB. It is from the same people who
made/make FlexES. It emulates both DASD and Tape (FakeTape(tm) and AWS
format) on a PC. Unfortunately, it is ESCON only, no FICON.
No, we don't use it here. No, I don't work for them. No, I don't get a
commission. <GRIN>
If IBM were to create a way to have a "virtual tape", then I really hope
that most of the code driving it could be run on a zIIP and/or zAAP and
not only on a general CP. We had CA's "virtual tape" (VTAPE) here and it
could use up a good chunk of CPU at times. That's why it is not here any
more. I was not directly involved with VTAPE, so I don't know if this
CPU usage was due to VTAPE or our implementation of it. From what I
understand, the VTAPE virtual tape was originally in VSAM files, but CA
was working on allowing the use of sequential files. Perhaps if they get
that working, they could optionally support AWS format virtual tapes (at
least for input). Or, horrors, they might document their VTAPE format so
that some other person could write a conversion program between VTAPE
formatted virtual tapes and AWS formatted virtual tapes. No offense to
CA, but software vendors in general don't seem to want to document much
of anything that they aren't forced to. That's why I love FOSS (Linux et
al.). Reminds me of the "glory days" of OS/360.
--
John McKown
Senior Systems Programmer
HealthMarkets
Keeping the Promise of Affordable Coverage
Administrative Services Group
Information Technology
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