W dniu 29.11.2023 o 04:56, Mark Zelden pisze:
On Thu, 23 Nov 2023 14:20:51 -0600, Jon Perryman<[email protected]> wrote:
On Wed, 22 Nov 2023 22:35:13 +0000, Seymour J Metz<[email protected]> wrote:
I suspect that there was a game of telegraph, whereby crucial details got lost.
It is normal to allocate page datasets in a user catalog that will eventually
be used as a master catalog.
I'm suspicious of the claim that z/OS can use a page dataset that is not in
its own master catalog, but I can't rule it out.
There are definitely crucial details lost. Page and swap are special datasets.
For instance, a page dataset can be in multiple catalogs (I think using
recatalog).
Pagespace can be in multiple catalogs (which should be a master to the system
that is using it) via
RECATALOG. I think at one time it had to have a HLQ of PAGE or SYS1 but my
memory is fuzzy on
that part. I know for a long time the HLQ doesn't matter at all for pagespace
and it could still be in
multiple catalogs. This also applies to swapspace and VSAM linear ZFS that is
indirectly cataloged.
Any SYS1 VSAM dataset can be in multiple catalogs via recatalog.
Don't ask me where this is documented now. :) I'm guessing "DFSMS managing
catalogs".
I dare to correct the above considerations.
1. Any non-VSAM and non-SMS dataset can be catalogued twice or multiple
times. Reason is obvious: there is no backward reference. It is just
entry in BCS, which contains DSN, UNIT and VOLSER.
2. VSAM datasets *cannot* be catalogued multiple times. And there is a
way to enforce it - VVDS.
3. IBM created exceptions for the 2. but only for SYS1 and PAGE HLQ.
Note - this is matter or HLQ, not VSAM type or flavour. In other words
one can "multi-catalog" any SYS1.VSAM.DSN regardless of its purpose and
any PAGE.VSAM.DSN, also regardless of its purpose.
4. Page dataset is specific kind of VSAM, because it is somehow
formatted before use. As one may know DEF PAGE takes significantly more
time than regular DEF CL and depends on its size.
5. So, it is still possible to have good reason to create some page
datasets, even cataloged in UCAT, but for future use. And future use
will require page datasets to be in MCAT. How? a) recatalog. b) my
current UCAT is de facto other system's MCAT. Other scenarios may apply.
My €0.02
--
Radoslaw Skorupka
Lodz, Poland
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