On Apr 20, 2006, at 2:18 PM, Gill, Geoffrey L. wrote:

...
So I think the question still remains how to reach that upper limit
instead
of the lower? Is there a TSM setting I have missed? Is there a
drive setting
that needs adjusting on the drive itself? ...

Geoff -

You are taking the moral equivalent of a default in using
FORMAT=DRIVE in your devclass. If the stars are in alignment, this
will work to get the most of of your tapes drives; but there are
circumstances where it won't, and in any case it's a vague
specification which departs from my long term, experience based rule
that it is always best to tell the system exactly what you want,
rather than let it make a decision and make its result indeterminate.
So, I would instead specify FORMAT=ULTRIUMC, which is explicit. (This
is the approach IBM takes in their Technote 1082581.) This will
provide the assurance that you are getting what you want. If, with
the next freshly started and then filled tape, you see no improved
capacity, it surely indicates that the data is rather incompressible.

Note that you can verify that compression is on in a tape drive by
issuing an OS query for its attributes.

  Richard Sims