> I'd like to know if there is somebody who already copied  8 mm tape used
> by adsm with unix utility ( I run on RS/600 H0 Aix 3.2.5 ) ?

You can always use 'dd' to duplicate tapes, assuming
that you have appropriate drives and media to have the new and
old tape mounted simultaneously.

> Is there somebody who expirimented this
> procedure... I'd like to know : 1) How he do this

dd if=/dev/rmt0 of=/dev/rmt1

Note that you need to use the raw devices, as that allows you to
take arbitrary sized chunks w/o worrying about blocksize on the
input tape.

> 2 )  Hown long times
> to do this

Close to 2 hours for an older Exabyte drive. 8mm drives are not
at all fast, especially if you use a verify pass to ensure the
tapes are identical.

> 3) Is a good procedure ?

Having duplicate copies of important data is *never* a bad idea.
8mm media is not as reliable as the 1/2" technology, so it's
doubly important to have redundant copies.

I'd recommend duplicating the tapes when they reach 60-70%
capacity, especially archive data, which tends to be more
difficult to reproduce. In no case should you rely on 8mm media
for more than 8-9 months unless you have incredibly good tape
storage facilities with precise humidity and temperature
controls. 8mm tapes are much more sensitive to environment, and
you have a lot more to lose if one goes bad. The ADSM AUDIT VOLUME
command can cope with some pretty ugly stuff, but it's not
impervious to errors.