I have been a bit of experimenting with z/OS QSAM files from a Cobol program and I find that the manuals don't exactly agree with my results. The manuals seem to imply that if you use the BLOCK CONTAINS clause (whether 0 or something else) then the file has a RECFM of either VB or FB. And if you don't include it then it's either V or B.
However, I have been able to read and write to a RECFM=VB file with a Cobol program that does not have the BLOCK CONTAINS clause. Additionally, I can read a RECFM=V file with a Cobol program that *does* have a BLOCK CONTAINS clause. I also can read and write files where BLOCK CONTAINS is specified (non-zero) but does not match the actual block size of the file. It just does not appear to matter. It seems to me that the RECFM and BLKSIZE information that is specified on the DD or in the catalog overrides whatever you tell Cobol anyway, so it seems to not matter what you tell Cobol. Basically (and I know this is something so small that you'd wonder why I even care) I can't see any reason to ever specify the BLOCK CONTAINS clause. If the file is already cataloged I definitely don't need it. And even if I want to create a new VB or FB file I can just put the RECFM option on the DD. One thing I haven't checked is if tapes will cause me any problems. But our applications all backup to disk files instead of tape, so I'm not really concerned. If you do wonder why I care, it's this... We are migrating from VSE to z/OS, and at the same time we are going to convert most of our existing ESDS files to regular sequential files. I see no reason to add "BLOCK CONTAINS 0" to all of our FD's if it has no affect (our VSAM FD's do not (generally!) specify the BLOCK CONTAINS clause, because it has no meaning to VSAM). (Yes, I do know we need to remove the AS- prefix from the ASSIGN clause of the SELECT statement.) Thanks! Frank ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
