Backups that write to tape are hanging. A review of the bptm log file shows SCSI error messages.

Overview:
Backups that write to tape are hanging.  A review of the bptm log file shows SCSI error messages.


Troubleshooting:
Review the NetBackup bptm log file and the /var/adm/messages log.  

Log Files:  
/var/adm/messages log shows the following message:

bptm[9879]: [ID 832037 daemon.error] scsi command failed, may be timeout, scsi_pkt.us_reason = 3

Resolution:
The error message seen in the /var/admin/messages log is NetBackup reporting a hardware issue.  
A review of the SCSI reason codes shows the following (bold added for clarity):

/usr/include/sys/scsi/scsi_pkt.h
/* * Definitions for the pkt_reason field. */
/* * Following defines are generic. */
#define CMD_CMPLT 0 /* no transport errors- normal completion */
#define CMD_INCOMPLETE 1 /* transport stopped with not normal state */
#define CMD_DMA_DERR 2 /* dma direction error occurred */
#define CMD_TRAN_ERR 3 /* unspecified transport error */
#define CMD_RESET 4 /* Target completed hard reset sequence */
#define CMD_ABORTED 5 /* Command transport aborted on request */
#define CMD_TERMINATED 22 /* Command transport terminated on request */
#define CMD_TIMEOUT 6 /* Command timed out */
#define CMD_DATA_OVR 7 /* Data Overrun */
#define CMD_CMD_OVR 8 /* Command Overrun */
#define CMD_STS_OVR 9 /* Status Overrun */

As shown, an Error 3 is an "unspecified transport error".  In this case, NetBackup is reporting problems with the hardware.  It is necessary to review the hardware environment and drivers, and determine what is causing this transport error.  If necessary, contact the hardware vendor to troubleshoot the issue and confirm the current firmware versions are properly installed.