With RECFM=U what you see is what you get. You will receive whatever is on the disk in a physical block. (Let's skip what is really happening under the covers in modern DASD.) You will get whatever was written. If it is a well-formed block written by QSAM RECFM=VB, or written with BSAM or even EXCP by a competent programmer "emulating" well-formed RECFM=VB, then yes, you will get a BDW followed by one or more RDW+record, with BDW = sum of all RDWs plus 4. If something else was written you will get that.
>From QSAM's point of view, yes RECFM=U is one record per block, or, depending >on which explanation you choose, no records and only blocks. Whether whoever wrote it viewed things differently is an unanswerable question. Whether they were that competent programmer is an unanswerable question. Whether you choose to view things differently is its own question. You might choose to "deblock" the data in any way you chose. You might write a "dump" program that dealt with the data one byte at a time, with no other structure. It is still hard for me to picture the question to which BSAM is the answer. In 1975, yes, I wrote a marvelous "database" system which used BSAM under the covers. In 2016 it's hard for me to picture. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Reichman Joseph Sent: Tuesday, July 19, 2016 8:16 AM To: [email protected] Subject: Re: Bsam VS Qsam for VB records With RECFM=U there is 1 record per block and the BDW is RDW + 4 ? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
