On Tue, 16 Dec 2014 16:19:20 -0500, Robert A. Rosenberg wrote: > >The limit should be 32763. That allows a 32767 byte VB (or VBS) >block. With a VB, there is room in a block for the 4 byte BDW and a >5-32763 byte V record (4 byte RDW plus 1-32759 of data). Why the >32760 LRECL Limit I do not know since that wastes 3 bytes in a VB >single record record block. > The limit should be 32767. Let me explain for the numerically challenged:
Suppose I have RECFM=VBS,BLKSIZE=10929,LRECL=32767. I can write 3 blocks, each consisting of: o A BDW (4 bytes) o A SDW (4 bytes) o 10921 bytes of data (total 10929 bytes). The first SDW should indicate that it's an initial segment; the second that it's an interior segment, the last a final segment. The total data are 10921 * 3; 32763 bytes. But LRECL always counts a 4-byte RDW, for a total of 32767. (If the RDW is not to be counted, add another block with 4 bytes of data (a 12-byte block) .) It was explained to me here that page alignment considerations impel buffers a multiple of 4KiB, and that there are a few bytes of overhead, and doubleword alignment considerations impel 32760. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
