Quoting David DeCuir <David.Decuir AT CLUBCORP DOT COM>:

> additional info if it helps:
> data per tape is either all NT or all UNIX
> mostly small files on NT
> about half small files on UNIX and half Oracle database files (2-20gb)
>
> The reason I ask is that my best guess seems to be such a wide range -
> I
> think between 60 and 150 gb per tape.
> Also, according to est. cap. and pct util, UNIX volumes shows about
> twice
> the capacity of NT volumes

Oracle .dbf files are initially allocated at a pre-specified size and
populated with long runs of zero bytes. Some of the zero bytes are
replaced with real data as applications write to the database. A .dbf
file with a generous allocation may still consist mostly of long runs
of zero bytes even after it has been in use for a while. Compression
algorithms can achieve results much better than the typical three to
one when working on long runs of zero bytes.