>     This can't be true, all my devc EST-CAPACITY are at 0, and I'm
>     certainly writing to tapes, besides the admin guide states that the
>     parm is optional.  Or is zero a 'special case'?

Indeed.  ESTCAPacity is a value you can change for amusement, or if you
want reports of as-yet-unfilled tapes to reflect their ultimate capacity;
but it is the true, physical capacity of the tape which ultimately
prevails, as EOT is finally hit and the tape is truly filled.
For example, fresh 3590 tapes show an ESTCAPacity of 10,000.0 MB, but
actually go to a significantly higher value as uncompressed or undercompressed
data fills them.         Richard Sims, Boston University OIT