Keep trying decrementing by 1 until you get the straddling case, I. E. 80,n = 1 track, 80,n+1 = 2 tracks.
On Tue, Mar 23, 2021 at 3:11 AM David Staudacher <[email protected]> wrote: > > I've looked over all the IBM-MAIN posts referring to AVGREC and don't see > that anyone has ever brought this up before. > I've read the relevant manuals, so I'm familiar with AVGREC syntax and how > it's supposed to work. > My concern is how to explain the differences in size allocation using > BLKS/TRK/CYL allocation and what *should be* the AVGREC equivalent, according > to the reference manuals (e.g. z/OS 2.4 MVS JCL Reference "AVGREC Parameter" > http://ibm.com/support/knowledgecenter/SSLTBW_2.4.0/com.ibm.zos.v2r4.ieab600/xddavgr.htm > ) > The discrepancies are consistent across multiple z/OS systems at different > sites, so I'm certain it is not site-specific. > Case 1 - SPACE=(TRK,1),DCB=(RECFM=FB,LRECL=80,BLKSIZE=27920) > With these specs and a 3390 (emulated) Device Type, the file will hold > *exactly* 698 records. > These 698 records are then copied to a second file allocated using these > specs: > AVGREC=U,SPACE=(80,698),DCB=(RECFM=FB,LRECL=80,BLKSIZE=27920),DISP=(,CATLG) > But instead of occupying 1 track, the new file occupies 2 tracks. Why? > Case 2 - SPACE=(TRK,1),DCB=(RECFM=F,LRECL=27920) > Basically same as above - still 1 track - except now with only 2 records. > And again, if these 2 records are copied to second file using > AVGREC=U,SPACE=(27920,2),DCB=(RECFM=F,LRECL=27920),DISP=(,CATLG) > the new file occupies 2 tracks instead of 1. Why? > So far, I've run many test cases copying existing files to new files using > AVGREC and in every case, when the existing allocation is completely full, > the size allocated to the copy is *always* larger than what is necessary to > accommodate the input file. In the case of a 100 cylinder input file, the > excess allocation is over 13 cylinders! > I have no explanation for this behavior, so I'm hoping someone here will. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
