Extended data sets all have an extra 32-byte "suffix" added to the end of the data field and 32 is added silently to the user-specified block size. The suffix has info in it that is used, inter alia, to guarantee that blocks received over telecommunication lines for mirroring purposes that may not be sent or received in the same sequence that the user wrote them will be destaged in the correct time sequence at the secondary volume's end. I believe this technology was spawned by XRC.
If you're using BSAM, you could just as easily add 32 to the blocksize and manage the "suffix" at the end of the buffer yourself. There's no need for the access method to do only these two new extra things for you. Either there are other reasons for supporting only extended data sets or else it's more of IBM's way of gently migrating all their customers to their newer, later, greater, and more profitable technology. And if they have supported it in BSAM, I expect QSAM will be happening pretty soon. Bill Fairchild Programmer Rocket Software 408 Chamberlain Park Lane * Franklin, TN 37069-2526 * USA t: +1.617.614.4503 * e: bfairch...@rocketsoftware.com * w: www.rocketsoftware.com -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Paul Gilmartin Sent: Thursday, September 13, 2012 9:40 AM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Data spaces vs hiperspaces On Sep 13, 2012, at 08:12, Bill Fairchild wrote: > Try Googling for a simple sample program using EXCP. I'm sure there must be > several on the CBT tape. I think you would have to use EXCP rather than BSAM > since BSAM apparently only supports 64-bit buffer addresses for extended data > sets, and your data set may not be extended. > Sheesh! They couldn't make an old-style data set a special case of an extended data set, and/of then couldn't treat a below-the-bar buffer as a special case of a 64-bit-addressable buffer? Conway's Law. Sigh. What does an extended data set use in place of CCHHR? -- gil
