Limit on the maximum number of cylinders for a DSN?

Virtual Storage Access method - ESDS, KSDS, RRDS & LDS. Basic direct access method, Basic sequential -, Queued sequential -, Basic partitioned -, Indexed sequential -, Object - access method.
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Ankuar Sapra
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Limit on the maximum number of cylinders for a DSN?

Post by Ankuar Sapra »

Hello All,

Is there a limit on the maximum number of cylinders that can be used to define a DSN? Or actually what is the maximum number of cylinders that can be used to define a dataset? Here I am considering the VSAM EXTENDED datasets. I tried allocating a dataset with SPACE=CYL(4500 4500) but I got:

Code: Select all

IGD17273I ALLOCATION HAS FAILED FOR ALL VOLUMES.
every time.

Maximum I was able to allocate with CYL(4350 4350).

Thanks.
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Robert Sample
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Re: Limit on the maximum number of cylinders for a DSN?

Post by Robert Sample »

This is one of those questions that can only partially be answered on a forum. The final answer must come from your site support group because different sites do things differently.

The most common disk in use on z/OS these days is a 3390, which comes in various sizes (3390 mod 3 or 3390-3 has 3335 cylinders, 3390 mod 9 or 3390-9 has 10015 cylinders, 3390 mod 27 and 54 (both of which are not official names but commonly used terms for extended volumes). So depending on how your site is set up, you may not be able to get more than 3335 cylinders in a primary allocation. Granted, this is being fairly rare these days but the devices are still out there.

I suspect your problem is that a data set, unless set up as an extended data set, is limited to 4,369 cylinders on a single disk volume. Why 4,369? Because 4,369 cylinders times 15 tracks per cylinder is 65,535 tracks and the limit for a single non-extended data set on a single volume is 65,535 tracks. How do you get past this limit? By talking to your site support group and finding out the site standard for extended data sets. The name to use will vary by site, so nobody on this forum can tell you what to use.
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Robert Sample
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Re: Limit on the maximum number of cylinders for a DSN?

Post by Robert Sample »

I just noticed you specified VSAM. Did you use the right data class in the DEFINE CLUSTER? You need to verify the name with your site support group. For sequential data sets, the limit for DSNTYPE=LARGE is 16,777,215 tracks or 1,118,481 cylinders per volume and up to 59 DASD volumes.
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