On Thu, 19 Nov 2015 15:59:37 +0000, J O Skip Robinson wrote:

>I haven't experimented with this, but going with NOSCRATCH is likely to 
>cause big problems with DASD GDGs. A data set residing on an SMS-managed 
>volume must be cataloged.

It has been a long time since I looked at this, but what I remember is 
that GDGs were a special case. For one thing, with SMS, a data set is 
cataloged at allocation time, not at step end like it was before.

One consequence of that is that is that a generation may be scratched 
as soon as the new one is allocated, rather than wait until the step 
ends successfully.

Consider a new GDG created with NEW,CATLG,DELETE. Before SMS, the 
old generation was scratched at the time the new one is cataloged at 
the end of the step, when the new one is cataloged.

As a result, the idea of a generation being rolled in and rolled out was 
created. The data set is cataloged, but is not cataloged as part of the 
GDG.

-- 
Tom Marchant

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