RE: TAP Statistics

["Richard Jackson" <richardjackson@xxxxxxxxxxxxxxxxxx>]

Al:

Think about it this way.  If you do DSPTAP, it will tell you the block size
for each saved file.  If you read through the tape drive manual, somewhere
in there it will tell you how large the inter-record gap is - used to be
three quarters of an inch but probably isn't any more.  If you know the
block size and the writing density, you can figure out how long each data
block is.  Each data block is followed by a IRG.  So data length plus IRG
equals bytes per unit distance.  This will probably work exactly the same
for all save files because they probably have the same block size.  If you
know how long the tape on the cartridge is, then you can figure out how much
it will hold.  Go back to the DSPTAP listing and add up the bytes for all
the stuff stored on the tape.  Compute the tape length to hold that amount
of stuff.  Subtract the used amount from the total amount.  That tells you
about how much tape you have in each cartridge that isn't being used.

This is all very simple unless the tape organization isn't
data-IRG-data-IRG-... anymore.  Helical writing or some other system could
foul up the approach.  I believe that existing cartridge tape drives store
36 bits at a wack - something else to consider.

The other problem with reel tapes - sometimes, the tape gets frazzled 250
feet in and you strip off the 250 feet and throw it away the  affix a new
tape mark and init the tape.  Then a 2,400 foot reel isn't 2,400 feet of
tape any more.  That is what I was referring to.  Of course, that was silly.
Who would use reel tapes anymore?

I used to give tapes to a guy who ran them through a tape cleaner.  I looked
like a huge tape drive with a microscope.  When the cleaner found a bad
spot, it would drag the tape back and forth over a razor blade to clean off
the crud.  If that didn't work, it would position the bad spot under the
microscope and he would scrape the bad spot off with a scalpel.  This
usually worked but when it didn't, we would chop off the tape at the bad
spot, affix a new tape mark, and init the tape.  Can you imagine anyone
actually doing this?  Can you imagine that we had a guy whose job
description was "tape librarian" who did this along with putting away tapes
created by jobs and getting out tapes that were input to other jobs?  And
those were 800 and 1600 BPI tapes!  Things have improved a little since
those days.

Richard Jackson
mailto:richardjackson@richardjackson.net
http://www.richardjacksonltd.com
Voice: 1 (303) 808-8058
Fax:   1 (303) 663-4325

-----Original Message-----
From: owner-midrange-l@midrange.com
[mailto:owner-midrange-l@midrange.com]On Behalf Of MacWheel99@aol.com
Sent: Tuesday, September 05, 2000 2:21 PM
To: MIDRANGE-L@midrange.com
Subject: RE: TAP Statistics


We use tape CARTRIDGES not a reel.  I believe there is a retentioning that
goes on but I guess if I change the SAVE to use *LEAVE & not the *REWIND
default, your suggestion might help me.  Thanks.

I use that on cartons of paper ... it so happens that our paper is 27
centimeters deep & 2700 sheets of paper to a carton, so I saw the
relationship of 100 sheets to the centimeter, but when I was looking at
paper
supply in inches, I never saw it.

From:   richardjackson@richardjackson.net (Richard Jackson)

Al, can you tell how many feet of tape are on a reel?  The other part is
pretty easy.

Richard Jackson
mailto:richardjackson@richardjackson.net
http://www.richardjacksonltd.com
Voice: 1 (303) 808-8058
Fax:   1 (303) 663-4325

-----Original Message-----
On Behalf Of MacWheel99@aol.com
Sent: Tuesday, September 05, 2000 11:52 AM
Subject: TAP Statistics

We use some tapes for end fiscal off load random volumes of old traffic
off_line, in which it is not predictable what the size of the old files will
be ... example our ERP keeps inventory transactions that are X months old &
the items with no recent activity keeps last Y transactions, so with steady
business the off loading is even volumes of transactions, but with
fluctuating customer base, the off-loads can vary greatly.

We would like to maximize what goes on one tape without the hassle of
multi-volume.

Is there an easy way in DSPTAP DMPTAP etc. to total up sizes of files there
& get a human intelligible figure like .... 30 files totalling 2 Gig ... 1/2
gig left on this tape?

I find myself at adding machine multiplying # records times byte sectors to
get total consumption of each file, then adding up each total to get total
tape consumed.  There's gotta be a better way.

Al Macintyre  ©¿©

Al Macintyre  ©¿©
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