Re: Duplicating 5 tapes takes 6?????

Paul, et al...

thing with tape that's different than say a CD/DVD is that tape handles
errors better...it writes a block, then tries to write a second
block...and if that second block is  a few meters down the way, so beit...

I would check your EREP for tape errors on both media and the device...and
when was the last time the tape unit was cleaned???


Don in DC

Home of JAM 2004 - The OS/400 and AIXL technical conference
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On Mon, 12 Jul 2004, PaulMmn wrote:

> I know it's been over a month, but I'm just catching up on some email...
>
> Not all tapes are the same length; the 1000' (example) tape in a
> cartridge is probably +/-  X% due to manufacturing tolerances (or a
> manufacturer trying to save a foot or so of tape here and there).  So
> original #1 may hold more data than duplicate #1, and so on.
>
> You'll could end up with a piece of the data from tape #1 on dupe #2;
> a bigger piece from tape #2 on dupe#3, and so on.  If your original
> save used almost all of tape #5, some of the data would get pushed
> onto tape #6.
>
> That's why you can't just duplicate each tape separately-- DUPTAP has
> to read the entire set in sequence as it creates the duplicate on
> another drive.
>
> You can check this out-- do a DSPTAP of all tapes from both sets and
> count the data blocks on the original set and the duplicate set.  The
> totals should match.
>
> --Paul E Musselman
> PaulMmn@xxxxxxxxxxxxxxxxxxxx
>
>
> >We have the 3570 tape library.  Our full system save takes 5 tapes.  After
> >the last full save, I used the DUPTAP command like always to make a
> >duplicate copy.  I ended up needing 6 tapes for the duplication.
> >
> >Anybody seen this before?  How/why would six tapes be used when duplicating
> >5?
> >
> >Note: BRMS is not used.
> >
> >Thanks,
> >Charles
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