After several decades of using MVS I finally ran into a case where I
thought GDS/GDG versioning might be useful and used it to create a
corrected version of a GDS generation using V01 to make it obvious it
was a corrected version.
I was lucky and didn't shoot myself in the foot. Somehow I was thinking
there would be an opportunity to verify things were cool before trashing
the GnnnnV00 version, but the instant the GnnnnV01 version is cataloged
the corresponding Gnnnnv00 version scratches! The only safe way to use
this feature if the original V00 is needed to generate V01 is to first
generate a new version of the GDS under an intermediate name, verify
correctness, then copy it back with the intended GnnnnV01 GDS name,
which means at that point you could instead just as easily copy it back
under the original GnnnnV00 name.
The only possible advantage to using Vnn > V00 to replace a V00 version
is that there is probably no time during which there is not some version
of that generation of the GDG in existence, as opposed to having that
generation disappear for the time it takes to delete the old GnnnnV00,
build the new data set, and catalog the new GnnnnV00 version. I concede
there might be some contexts in which that slight difference in behavior
might be important. I just never encountered one in practice.
Joel C. Ewing
On 11/17/2015 08:04 PM, Ted MacNEIL wrote:
> Versioning
>
>
> -
> -teD
> -
> Original Message
> From: Peter Hunkeler
> Sent: Tuesday, November 17, 2015 16:42
> To: [email protected]
> Reply To: IBM Mainframe Discussion List
> Subject: AW: Re: Fastest way to read OLDEST GDG entry
>
>> What makes "V00" ever Vnn, where N<>0?
>
> IIRC, the system does not really care for the version number. When a new GDS
> is allocated using relative numbering, the version is always V00. If you want
> to replace a GDS with a specific generation number while keeping the place in
> the GDG, you cataloge the new data set using the fully qualified DSN but
> replace the V00 with whatever version you like. The new data set will become
> a GDS in place and at the place of the V00 GDS. This new GDS will be treated
> as any other GDS, i.e. aged and eventually rolled off.
>
>
> I don't see practical use for this.
>
>
> --
> Peter Hunkeler
>
>
--
Joel C. Ewing, Bentonville, AR [email protected]
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