We use a HP1553 with ADSM V2M6R12 on OS/2 WARP and it has a nice display
that says about compression. When we use the hardward compression it's
actualy making the files bigger (harware compression factor 0.9). Probably
because our clients are compressing the files on backup.

So we switched off the hardware compression (using DDS2 and not DDS2C as
format)

Gerhard




Usually, once a label is written you can't change the format on the tape
without bulk erasing the label and starting over again.  I know this is the
case with DLT media and am extrapolating that knowledge to your situation.
 You certainly can't write both compressed and non-compressed data on the
same tape.

Just my ideas but with no foundation.

Kelly