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
