Yep been there done that with setting DVC to 59 causing a banking application, 
PEP+, to exhaust the TIOT.  The TIOT was set to the maximum value.



"Confidentially doc, I am the wabbit."

Bugs Bunny

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On Friday, April 4th, 2025 at 10:51 AM, Michael Watkins 
<[email protected]> wrote:

> One idea might be to change the DATACLAS as follows: set column 14 'VOLUME 
> COUNT' to '1' and then set column 16 'DYNVOL COUNT' to '58'.
> 
> This prevents the catalog record from containing unused fields for DASD 
> volumes never allocated since only the volumes actually used will be 
> contained in the catalog.
> 
> However, this does use extra space in the TIOT. (Suggestion: Set TIOT size to 
> 64 in the ALLOCxx PARMLIB member.) Even with TIOT size 64, JOBSTEPs with over 
> 125 or so DD cards all specifying this DATACLAS will blow out the TIOT and 
> the job will fail.
> 
> -----Original Message-----
> From: IBM Mainframe Discussion List [email protected] On Behalf Of 
> Jousma, David
> 
> Sent: Friday, April 4, 2025 9:21 AM
> To: [email protected]
> Subject: Migrating Storage pools to EAV
> 
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> 
> So, we are finally biting the bullet and making 1TB EAV volumes our standard 
> for UCB relief, etc. One "habit" my Storage team over the years had done to 
> mask poor dataset allocations was to make the mainly used DATACLAS 
> multi-volume, with a max of 59 volumes. It was before my time, but I'm 99% 
> sure that was done to avoid x37 abends for max extents. Now that we are going 
> to EAV's, we'll be clearing off the mod-54's and DISNEW them. And with a 20-1 
> reduction in physical volumes, there will likely be pools that had say 100 
> volumes, that could end up with just 5 EAV's.
> 
> I'm not a storage guy by craft, so am wondering if there is any magic dust to 
> help with this other than making the owners of the poorly allocated files 
> make adjustments to their allocations?
> 
> Dave Jousma
> Vice President | Director, Technology Engineering
> 
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