Back in the day I was Senior German Engineer for Enterprise Technical-Support by Veritas.
I now see this tech-note http://www.symantec.com/business/support/index?pag... which is pretty much useless in 90% of cases.
The reason why you will get Event ID (SCSI sense key) 9, 11 or 15 is because one of the SCSI devices is configured for SCSI ID 6. Take it off ID 6 and put the tape device on ID 5 and your problem will be solved.
I thought I had tought the folks better, but it seems that what I told them has been forgotten,
BTW if anyone is interested the source of my wisdom, it comes from the German c't magazine issue 18 from 1998 page 193 column three onto four.