I was putting a different Compaq 35/70 DLT drive in place of an existing one. When I plugged it into the back of my SunFire 280R, same place the first one was plugged into, the system hung with Oracle users unable to continue. Oracle files were on /d02. Help me understand what may have gone wrong.
I made the LUN the same as the replaced drive (3).
The scsi cable had a smaller plug at the DLT end, but the same on the server end.
I mistakenly placed the terminator on the scsi-in port and the server on the scsi-out port. (Is this it?)

What I did to restore operational system:
Put the old DLT in place.
Could not determine a command to remount /d02 (or otherwise tell the system to retry and resume.)
After checking that the reboot command would synchronize the filesystem, I did a reboot, first one in a couple of years.
System came up fine.

Other info:
The dmesg shows this as the first console indicator of a problem:
Oct 30 11:07:02 nscsun2 Error for Command: read Error Level: Retryable
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] Requested Block: 639408 Error Block: 639408
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] Vendor: Symbios Serial Number: 9 $E g
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] Sense Key: Unit Attention
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] ASC: 0x29 (power on, reset, or bus reset occurred), ASCQ: 0x0, FRU: 0x0
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.warning] WARNING: /pci@8,700000/scsi@2/sd@a,0 (sd39):
Oct 30 11:07:02 nscsun2 Error for Command: write(10) Error Level: Retryable
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] Requested Block: 146907360 Error Block: 146907360
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] Vendor: Symbios Serial Number: 9 D
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] Sense Key: Unit Attention
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.notice] ASC: 0x2a (<vendor unique code 0x2a>), ASCQ: 0x1, FRU: 0x0
Oct 30 11:07:02 nscsun2 scsi: [ID 107833 kern.warning] WARNING: /pci@8,700000/scsi@2/sd@a,2 (sd117):
--------------------------
Other facts are shown by this output. What should I do about these, if any thing. They may have nothing to do with the system hanging and my DLT problem above.

bash-2.05# iostat -En
c0t6d0 Soft Errors: 4 Hard Errors: 0 Transport Errors: 0
Vendor: TOSHIBA Product: DVD-ROM SD-M1401 Revision: 1009 Serial No:
Size: 0.00GB <0 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 4 Predictive Failure Analysis: 0
c1t10d0 Soft Errors: 1 Hard Errors: 4 Transport Errors: 0
Vendor: Symbios Product: StorEDGE A1000 Revision: 0301 Serial No:
Size: 220.50GB <220498755584 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 4 Recoverable: 0
Illegal Request: 1 Predictive Failure Analysis: 0
c1t10d1 Soft Errors: 1 Hard Errors: 2 Transport Errors: 0
Vendor: Symbios Product: StorEDGE A1000 Revision: 0301 Serial No:
Size: 46.97GB <46974107648 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 2 Recoverable: 0
Illegal Request: 1 Predictive Failure Analysis: 0
c1t10d2 Soft Errors: 1 Hard Errors: 2 Transport Errors: 0
Vendor: Symbios Product: StorEDGE A1000 Revision: 0301 Serial No:
Size: 26.37GB <26369589248 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 2 Recoverable: 0
Illegal Request: 1 Predictive Failure Analysis: 0
c2t1d0 Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: FUJITSU Product: MAP3735F SUN72G Revision: 1201 Serial No: 0348Q0694V
Size: 73.40GB <73400057856 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 0 Predictive Failure Analysis: 0
c2t0d0 Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: FUJITSU Product: MAP3735F SUN72G Revision: 1601 Serial No: 0415Q09DGG
Size: 73.40GB <73400057856 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 0 Predictive Failure Analysis: 0


For the DLT issue and /d02 not being available, should I have just keyed
umount /d02
mount /d02 ?

Would that have avoided the reboot? I did try 'mount /d02', but os objected to that.

Thank you for assisting me.