There were "gapless" tapes generated by seismo trucks, used
for recording data from the geophones, normally seen as data
input for 3DFFTs. I last dealt with these 20+ years ago working
w/ oil exploration stuff. At the time triple-buffering and
multiactivity
(multithreading) was de rigeur.
The tape density wasn't incredibly high but it was a continuous
stream that you couldn't afford to drop since that'd require re-
starting the process.
--------------------
John R. Campbell, Speaker to Machines (GNUrd) {813-356|697}-5322
"Will Work for CLAIM Codes"
IBM Certified: IBM AIX 4.3 System Administration, System Support
John Summerfield <[EMAIL PROTECTED]>@VM.MARIST.EDU> on 04/18/2002
12:52:03 PM
Please respond to Linux on 390 Port <[EMAIL PROTECTED]>
Sent by: Linux on 390 Port <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
cc:
Subject: Re: How to pre-allocate a 4GB File?
> Jay Maynard wrote:
>
> >
> > The limit is that the cylinder number is a halfword, and exceeding that
> > breaks a LOT of things. There are even today things you can't put on a
> > 3390-9 beyond cylinder 65535 (the JES2 spool dataset springs
immediately to
> > mind).
>
>
> Minor nit. On MVS a single extent cannot exceed 65535 *tracks* and
> a 3390-9 has 10017 cylinders (150255 trks).
>
> Theoretically, ckd architecture can support 65535 cyls, 65535 heads
> (or trks/cyl), 255 blks/trk, each blk with a 255 byte key area and a
> 65535 byte data area (which adds up to a fairly large number).
>
> Greg
>
Not quite - the key for this purpose is included in the length of the
data block.
(65535 * 255 * 65535) is still fairly large. More than 2.3 Gbytes.
Back in my time the maximum data length supported on any device was
32k-8, but I did hear of someone reading an entire tape written (by
some metering device) as a single block.
--
Cheers
John Summerfield
Microsoft's most solid OS: http://www.geocities.com/rcwoolley/
Note: mail delivered to me is deemed to be intended for me, for my
disposition.
==============================
If you don't like being told you're wrong,
be right!
