My 'interested colleague' Meral Temel supplied a crucial piece of the puzzle. She filled up a volume totally with ordinary data sets to where external indicators showed zero tracks of free space. She then allocated a zero-space data set on the volume with no error. There could not have been a spot for any fragment of the data set to be written outside the VTOC.
I know that ISPF Browse will show 'no data' if it judges from the VTOC that utilization is zero, as in 3.2, regardless of what might be there physically. OTOH IEBGENER attempts read a file until EOF regardless of VTOC info. I ran GENER to print a zero-space data set:. The result is the same as if the only data on the first track were EOF. DATA SET UTILITY - GENERATE PROCESSING ENDED AT EOD . . JO.Skip Robinson SCE Infrastructure Technology Services Electric Dragon Team Paddler SHARE MVS Program Co-Manager 626-302-7535 Office 323-715-0595 Mobile jo.skip.robin...@sce.com From: Richard Peurifoy <r-peuri...@neo.tamu.edu> To: IBM-MAIN@LISTSERV.UA.EDU Date: 08/28/2012 01:33 PM Subject: Re: Space Allocation In Bytes Sent by: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On 8/28/2012 3:19 PM, glen herrmannsfeldt wrote: > Shmuel Metz , Seymour J. <shmuel+...@patriot.net> wrote: >> In <503bf5eb.5010...@bremultibank.com.pl>, on 08/28/2012 >> at 12:34 AM, "R.S." <r.skoru...@bremultibank.com.pl> said: > >>> Valid, but illogical. Data set with zero size is illogical. > >> No. > >>> That's exploitation of "side effect". Stilla valid (it works, so >>> it is valid), but it's still illogical. > >> It's perfectly logical, as are /dev/null and DUMMY. > > But for CKD doesn't there have to be some place to write the EOF? I think BSAM/QSAM will simulate an EOF without doing any I/O to the data set if you try to read it. -- RIchard ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
