I/O errors on LOCATE commands (timeouts) to DLT 4000 or 7000s indicate that
the DLT on-board directory was determined to be invalid and an alternate
search scheme was invoked.  Some time ago I received a device driver patch
from ADSM support to increase the timeout value for the LOCATE command on
DLT drives (known DLT issue).  I would recommend V85 microcode for DLT 7000s
(better/more directory error recovery).  If the directory is determined to
be invalid/bad, it will be reconstructed by reading through the entire tape
(can take up to 4 hours on DLT 7000).  You can check www.dlttape.com and
follow discussion threads on directory errors.

Error 46 usually indicates that the drive is not available (from an AIX
perspective, check SMIT).  You may want to make sure that the drives are
defined to automatically come available after AIX startup.  I have had
occasions, however, where the only way I could clear a 46 code was to go
into SMIT and delete and redefine the drives to AIX.

On the media faults, I would check to see if drive cleaning is set up
properly in the library (cleaning cartridge in proper slot, not used up,
etc.)