Using SCSI tapes

Is there something special you have to do to use a SCSI tape drive??  
I'm trying to help a friend try to use a SCSI tape drive (SDLT) on Hercules (3.06 on Linux) but we keep ending up with the tape drive "device or resource busy".  
Prior  to starting hercules I can use mt to control the tape drive (/dev/nst0) with no problem, but as soon as we try to use  it from Herc we get the  resource busy error, with lots of messages such as:
08:46:39 HHCTA024E Error opening 0:0560=/dev/nst0; errno=16: Device or resource busy
08:46:39 HHCCP048I 0560:CCW=07400001 00000000=>000A0000 00900074 40404040 F0F04040 ........    00  
08:46:39 HHCCP075I 0560:Stat=0E00 Count=0001
08:46:39 HHCCP076I 0560:Sense=50420022 00000020 00000000 00000000 00000000 00000000
08:46:39 HHCCP077I 0560:Sense=INTREQ EQC ITF WRI
The device is defined as:
0560      3480    /dev/nst0 --no-erg --blkid-32

Any suggestions?