Because that's not our problem. I thought I was answering the original poster's question and extended it out to the VTOC and repercussions there, along with possibly running out of space in the VTOC, which is why you might want to do DEFRAG.
Regards, Steve Thompson -----Original Message----- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Ron Hawkins Sent: Friday, March 05, 2010 3:29 PM To: IBM-MAIN@bama.ua.edu Subject: Re: Defrag 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 ---------------------------------------------------------------------- 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
