W dniu 27.07.2023 o 21:30, Wendell Lovewell pisze:
Hi Bill.
I can confirm that in a format-3 record with all 13 slots filled, the DS3PTRDS field
points to the CCHHR of the next format-3. And the "next" slot in the format-9
record then points to the next format-3.
I tried to confirm that there will be a second format-9 record for a file with >
133 extents. And that the DS9PTRDS field in the first format-9 will point to the
second format-9 record. But I've not been able to create a dataset with > 123
extents. I believe 255 are possible. From z/OS 2.5 DFSMS Using Data Sets:
"You can expand the space for a nonstriped VSAM component to 255 extents. For
SMS-managed VSAM data sets, this extent limit is removed if Extent Constraint Removal is
specified in the Data Class. The theoretical limit is then the maximum number of volumes
(59), times 123 extents per volume, or 7257 extents."
...so I don't know if > 123 extents is possible on a single volume.
Regarding the last sentence: NO.
VSAM and any other datasets are limited to 123 (or 16) extents per volume.
However regular PS file was limited to 16 (or 123 for extended format)
extents multiplied by number of volumes (up to 59). So the total number
of extents could be hundreds or more. But VSAM was limited to 255 total,
despite of how many volumes it took.
Now the limitations can be removed by DFSMS parameter. But the
limitation of 123 extents per volume is not relieved.
BTW: EAV/EAS did not change the limits of extents. Neither per volume,
nor per dataset.
--
Radoslaw Skorupka
Lodz, Poland
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