In a message dated 3/8/2007 2:50:24 P.M. Central Standard Time, [EMAIL PROTECTED] writes: >re: _http://www.garlic.com/~lynn/2007e.html#64_ (http://www.garlic.com/~lynn/2007e.html#64) FBA rant Please be more specific. There are about 100 articles on that web page. >for other drift ... if the geometry characteristics were to be ignored then you could treat the six byte seek argument as the track number (allowing the device to interpret the physical characteristics ... somewhat similar to what FBA does in the locate command for the record number). This is all quite true. But this doesn't answer my question. If there had been no 2321, then why would we need the first two bytes of the 6-byte seek address? I find it hard to believe that IBM in 1964 envisioned the day 40+ years into the future when they would need more than 4 bytes to describe uniquely a track on one device. Today I can see the limit drawing close. But not 40 years ago. >i.e. CKD seek command is six byte field _http://www.garlic.com/~lynn/gcard.html#26.1_ (http://www.garlic.com/~lynn/gcard.html#26.1) Please be more specific. There is about 100 articles on that web page. The fact that a seek command has a 6-byte data field transferred is not what I am asking about. I stipulate 6. I am asking why not 4? >and FBA locate command _http://www.garlic.com/~lynn/gcard.html#26.2_ (http://www.garlic.com/~lynn/gcard.html#26.2) is eight byte number, which could allow for 2**64 512-byte records (i.e. 2**9 times 2**64 bytes, 2**73 bytes per device) All quite true. But why did CKD (i.e., non-FBA) devices need the two extra bytes called bb except for the 2321? >for something complete different, quicky search engine use turned up this (IBM) patent reference on mapping tof CKD to native FBA hardware _http://www.patentstorm.us/patents/6112277-description.html_ (http://www.patentstorm.us/patents/6112277-description.html) Interesting, but I would rather stick to the subject I asked about. >Reference should be made to Menon, U.S. Pat. No. 5,301,304, "Emulating Records in One Record Format in Another Record Format", issued Apr. 5, 1994. Menon exemplifies the state of the art in format conversion disclosing an emulation method for rapidly accessing CKD records in which the CKD records are stored on a disk drive in FBA format. The bb was invented ca. 1964, not 1994. Why was there a bb except for the 2321? >now as suggested in previous post http://www.garlic.com/~lynn/2007e.html#46 FBA rant >what would be the difficulty in modifying whatever MVS calls its current incantation of CCWTRANS ... to morph application space EXCP CCWs that are still doing things like multi-track VTOC/PDS search into FBA operations ... aka there are hardware control units and hypervisor software that perform such morphing ... then if the original VS2 started out with (cp67's) CCWTRANS moved into the VS2 kernel ... why can't more current hypervisor technology be moved directly into the VS2 kernel >here is decade-plus old descriptive narative of ECKD (from vm mailing list) ... basically discussing the retrofitting FBA-like channel commands to CKD architecture: _http://listserv.uark.edu/scripts/wa.exe?A2=ind9604&L=ibmvm&T=0&P=9321_ (http://listserv.uark.edu/scripts/wa.exe?A2=ind9604&L=ibmvm&T=0&P=9321) More wonderful details that do not address my one and only question. The bb was invented long before ECKD and FBA. Why, other than for the 2321? >ECKD channel programs completely describe the nature and scope of data transfer operation before the first data transfer command is executed. These "predictive" channel programs "remove all possible surprise" from the storage subsystem during data transfer operations. Like Fixed-Block Architecture (FBA) DASD, ECKD uses the DEFINE EXTENT channel command to delimit the range of tracks which may be affected by a channel program. ECKD is still CKD: each record can contain Count, Key, and Data areas. However, the count need not be CCHHR, as on conventional CKD DASD; one could number the records sequentially, like FBA blocks. I know all that. Why is there the bb part of the bbcchh except for the 2321? >as opposed to post http://www.garlic.com/~lynn/2007e.html#40 FBA rant with my nearly 25yr old email commenting on ECKD _http://www.garlic.com/~lynn/2007e.html#email820907_ (http://www.garlic.com/~lynn/2007e.html#email820907) How about a post commenting on bb instead of things like ECKD, FBA, etc. etc.? Bill Fairchild Plainfield, IL
"Criticism and dissent are the indispensable antidote to major delusions." [Alan Barth, 1951; The Loyalty of Free Men] <BR><BR><BR>**************************************<BR> AOL now offers free email to everyone. Find out more about what's free from AOL at http://www.aol.com. ---------------------------------------------------------------------- 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
