The system structures designed into S/360 that turned into bottlenecks sooner than most others did were built around the cKd architecture, in which the K is uppercased because it means KEY (where "KEY rhymes with "bad, bad, bad"). Real key areas were written onto DASD tracks for system catalogs, PDS directories, VTOC records (DSCBs), PASSWORD data set (I think), all ISAM files, and users also had the capability of creating keyed records with physical keys in BDAM, BPAM, and SAM files if they wanted to. System catalogs were eventually replaced with VSAM structures, PDS directories were supposed to have been ameliorated with PDSEs, and VTOC keyed record searches were ameliorated with Indexed VTOCs. ISAM support was eventually dropped by IBM. All those keys seemed to make good sense in 1965, but not any more. No CKD DASDs have been manufactured, that I know of, for 15 or 20 years. Everything is FBA and RAID now. Hardware microcode emulates physical keys. Lots of operat! ing system software supports keys, which are still used sometimes as a lock controlling access to the record's data area. Some sophisticated users invented other clever uses for keys.
Bill Fairchild Software Developer Rocket Software 275 Grove Street * Newton, MA 02466-2272 * USA Tel: +1.617.614.4503 * Mobile: +1.508.341.1715 Email: [email protected] Web: www.rocketsoftware.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of McKown, John Sent: Thursday, February 11, 2010 7:37 AM To: [email protected] Subject: Re: PDS vs. PDSE Does anything other than S/360 derived systems even use CKD type DASD? PDS directories are built around CKD. And, in their day, moving the search logic out to the peripheral was probably a good idea. -- John McKown Systems Engineer IV IT ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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
