[Info-vax] 9 track end of tape (Was: Copying VMS SaveSet Under Windows)

[Alan Frisbie]

On 11/22/2010 2:23 PM, glen herrmannsfeldt wrote:

>> After the physical tape mark, there is some writable tape.  Once the
>> drive indicates that the physical mark has been reached, it is expected
>> that the software will finish the current block and then write a logical
>> end of tape.  There should be enough writable tape left for that.
>
> For reasonable blocksize, anyway.  There is a story of doing data
> chainging on S/360, such that a tape can be written with one
> very large block.

Around 1970 I had to deal with some of those tapes.   They were some
sort of seismographic data, and had been written on a Kennedy 
Incremental tape deck.   We had a program that would read the tape
on the slowest drive and write a copy (in reasonably-sized blocks)
to the fastest drive.   It took a bit of education to get the operators
to use the correct drives.

The other odd tapes we had to deal with had to be processed in
reverse order -- last record first.   The program would skip to
end-of-file, then enter a loop of backspace-backspace-read,
backspace-backspace-read, backspace-backspace-read...
The noise from the tape drive was frightening, and we were shortly
asked to refrain from running it on the S/360.

It was incidents like this which convinced management that we
needed our own mini-computer (Varian 620/i) lab for these
"special" jobs.   :-)

Alan (The Other AEF) Frisbie