It sounds like you are using the wrong device driver.  For 3570 devices, you
install Atape (or IBMtape for Solaris) and define the drives in smit
devices/Tape Drives, not devices/ADSM Devices.  So you should NOT have or use
/dev/mtX for these.   The Atape driver will return a "rmtX Available" message
as you define/configure them, and this is what you want.

The ADSM command is DEF DRIVE libname drivename DEVICE=/dev/rmtX ELEMENT=YY

X is the number given you by smit.  YY is required in a two-drive config.  The
drive elements are mapped in the 3575 hardware reference and may even be in the
ADSM pubs or readme.  Here you have to be careful to make sure your rmtX value
correctly matches your element number-  the only way to tie them together is
with the SCSI id.  So carefully record each drives' scsi ids, find the element
number for that drive in the element map, and as you define them  in smit
record the rmtX value for each one.

Craig Bell