Lynn, Of course you are correct as far as the physical disk is concerned, but z/OS only talks to ECKD controllers which emulate ECKD on FBA devices.
The discussion was on how BSAM and other I/O routines read and write data on DASD. Chris Blaicher Principal Software Engineer, Software Development Syncsort Incorporated 50 Tice Boulevard, Woodcliff Lake, NJ 07677 P: 201-930-8260 | M: 512-627-3803 E: cblaic...@syncsort.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Anne & Lynn Wheeler Sent: Thursday, December 25, 2014 8:58 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: BDW length vs. Physical Length cblaic...@syncsort.com (Blaicher, Christopher Y.) writes: > ECKD, which is what all modern DASD is, stands for Extended Count Key > Data. The 'Extended' refers to the channel commands you can issue, > not the devices capabilities. All blocks written to a ECKD device > consist of a Count field, an optional Key field and a Data field. The > Count field is 8 bytes long and has a format of CCHHRKDD. (Extended > format volume count fields are formatted slightly differently, but for > basics, this will do.) all modern disk is fixed-block, there hasn't been any real CKD DASD manufactured for decades ... it is all emulated on industry fixed-block disks. ECKD started out when MVS couldn't support FBA ... and they wanted to retrofit 3380 3mbyte/sec disks to 168&3033 1.5mbyte/sec channels ... getting CALYPSO to work was something of horror story past posts mentioning FBA, CKD, multi-track seek, etc http://www.garlic.com/~lynn/submain.html#dasd past posts specifically mentioning CALYPSO http://www.garlic.com/~lynn/2004o.html#7 Integer types for 128-bit addressing http://www.garlic.com/~lynn/2007e.html#40 FBA rant http://www.garlic.com/~lynn/2007f.html#0 FBA rant http://www.garlic.com/~lynn/2008q.html#40 TOPS-10 http://www.garlic.com/~lynn/2009k.html#44 Z/VM support for FBA devices was Re: z/OS support of HMC's 3270 emulation? http://www.garlic.com/~lynn/2009p.html#11 Secret Service plans IT reboot http://www.garlic.com/~lynn/2010e.html#36 What was old is new again (water chilled) http://www.garlic.com/~lynn/2010h.html#30 45 years of Mainframe http://www.garlic.com/~lynn/2010n.html#14 Mainframe Slang terms http://www.garlic.com/~lynn/2011e.html#35 junking CKD; was "Social Security Confronts IT Obsolescence" http://www.garlic.com/~lynn/2012j.html#12 Can anybody give me a clear idea about Cloud Computing in MAINFRAME ? http://www.garlic.com/~lynn/2012o.html#64 Random thoughts: Low power, High performance -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ________________________________ ATTENTION: ----- The information contained in this message (including any files transmitted with this message) may contain proprietary, trade secret or other confidential and/or legally privileged information. Any pricing information contained in this message or in any files transmitted with this message is always confidential and cannot be shared with any third parties without prior written approval from Syncsort. This message is intended to be read only by the individual or entity to whom it is addressed or by their designee. If the reader of this message is not the intended recipient, you are on notice that any use, disclosure, copying or distribution of this message, in any form, is strictly prohibited. If you have received this message in error, please immediately notify the sender and/or Syncsort and destroy all copies of this message in your possession, custody or control. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
