Steve, Why not just allocate a bigger VTOC. The argument is that the regular shuffling of thousands of CYls into contiguous extents to save one or two cyls on a VTOC is valuable exercise.
I don't see it. I would give the Storage Admin help and guidance on sizing a VTOC, and how to reallocate a larger one. Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of > Thompson, Steve > Sent: Friday, March 05, 2010 10:47 AM > To: IBM-MAIN@bama.ua.edu > Subject: Re: [IBM-MAIN] Defrag > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On > Behalf Of Rick Fochtman > Sent: Friday, March 05, 2010 12:33 PM > To: IBM-MAIN@bama.ua.edu > Subject: Re: Defrag > > ----------------------------------<snip>-------------------------------- > ------ > AFAIK, you are limited to 16 extents on a volume (NON-VSAM, PDS, DAM, > etc.). If you are allowed (or can) do multi-volume, then yes, you get 16 > > [max] per volume for 59 volumes. > > Reclaiming space in the VTOC: If I can get all my space consolidated to > just the DSCB #1, then all the other DSCBs (model 3s) become available, > giving space for more allocations in the VTOC. If I remember correctly, > there can be up to 4 Model 3 DSCBs to get you to 16 extents (for a data > set) -- (non-VSAM, PDS, DAM, PS, etc.). Otherwise, once you have used up > > all the DSCBs in the VTOC, you can't allocate anything more, or even get > > a secondary extent on that volume. So defragging does recover space for > a VTOC. > --------------------------------<unsnip>-------------------------------- > ------ > I can't speak for Extended Format, but for non-Extended Format datasets, > > you can only have one FORMAT-3 DSCB per dataset (Except for the special > case of ISAM, now long dead.) > > Rick > <SNIP> > > Based on the doc, if an F1DSCB can only have 3 extents, and an F4DSCB > can only have 4 extents, but a simple PS data set is limited to 16 > Extents on a volume, then we have a problem. > > It has been 14+ years since I've had to do DSCB handling (OBS/ACS WYLBUR > would try to get a PDS to a single extent...). So I don't recall the > actual layouts and only went by what IBM's doc says. And I could very > well have misread or misinterpreted DFP/DFSMS's verbiage. > > But the point was recovering space in a VTOC... > > Regards, > Steve Thompson > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO > Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
