>AH HA...I have experienced the same thing. I chased this with support and so 
>far
>I've gotten a working as designed answer...

So much for the design.  ;-)
Actually, the following players are involved in this scenario, and it may
be worth taking a look at relative levels:
  - TSM server
  - Operating system PTF level
  - SCSI device driver level (connection to tape drives)
  - Atape device driver
  - Atldd device driver
  - 3590 microcode level
  - 3494 microcode level
What appears in the operating system error log can be indicative.
In general, if the device-related code is at a higher level than the
host-related software that receives indications, the host-closer
software may fail to understand or misinterpret what the device-related
code is saying.
The 3494 itself has error logs, which your customer engineer can
inspect for anomalies - worth having him/her do the next time they
are in your shop, so save the date and time of the events.
With all the elements involved in the mix, trying to keep them all
compatible and happily interacting becomes a challenge, considering
all the other things we have to do.
    Richard Sims, BU