On Sat, 6 Oct 2012 21:39:13 -0400, Robert A. Rosenberg <[email protected]> wrote: > >There are 4 types of records in a VBS block (which are identified by >the segment descriptor bits). These are start of segment (the record >continues in the next block), end of segment (this is the end of a > You appear to have swapped the terms "record" and "segment" above, then switched to proper usage below.
>record that started in a prior block), middle segment (this record >started in a prior block and continues in the next block), and >complete record (a standard VB record which is totally contained in >the current block - it is signified by the lack of any segment bits >like all records in a VB block). > >... RDW ... RDW ...RDW... . > No. "SDW" in each case. If you disagree, please cite for me any specification, such as in "Using Data Sets", which mentions "RDW" in connection with RECFM=VBS data sets. This is not purely pedantic. The precise usage determines whether empty logical records may appear in a VBS data set. As I read it, they may not. >Note that when you are writing to DASD, the block size is restricted >to however much room is left on the track so the last block on a >track is shorter than the defined Blocksize. > I've been told elsewhere that only Binder (Linkage Editor?) performs such track balancing. Otherwise access methods will start a new track whenever there is insufficent space in the current track for BLKSIZE bytes. This could apply as well for RECFM=VB as for RECFM=VBS. This provides the rationale for SDB's choice of 32760 when RECFM=U and half track for any other RECFM (3380/3390). --gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
