Re: IDCAMS and DF/SORT support for LBI

On Thu, 14 Sep 2006 22:21:22 -0500, Tom Schmidt misspoke:

On Thu, 14 Sep 2006 18:29:19 -0400, Thompson, Steve (SCI TW) wrote:

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@xxxxxxxxxxxx
Behalf Of Tom Schmidt
Sent: Thursday, September 14, 2006 5:22 PM
To: IBM-MAIN@xxxxxxxxxxx
Subject: Re: IDCAMS and DF/SORT support for LBI

<snip>
LBI is limited to tapes, not DASD. (Too bad - I would like to see the
3390 geometry disposed of at long last. 3390's track length is getting
cramped.)
<snip>

The 3390 does not have a problem with LBI. IBM has a problem with DASD
and LBI. Something about the architecture of a DCB...

(Is it really the DCB that's the limit? I don't think so.)

The tapes use DCBs (and only DCBs) and they managed to overcome the 32760
byte limitation inherent in the original question here. 3390 uses either
DCBs or ACBs (a handy alternative, eh?) and the folks in San Jose have
worked some serious magic recently to mine unused and then underused bytes,
nybbles and bits out of the various I/O control blocks in order to provide
the somewhat recent support for million-plus track files on DASD.

All I'm asking is: since a 3390-54 is still anchored on 3390 geometry,
isn't it time yet to expand that (virtual) track length to something
vaguely similar to the underlying shark disks?

Or, better yet, bring out a new DASD architecture. Maybe FBA or maybe (by
now) something better.

The "(and only DCBs)" is an overstatement, I think. DCBs and DCBEs might
be closer to reality.

(And now, back to your regularly scheduled comedians...)
--
Tom Schmidt
Madison, WI

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