The commands to scan and discover attached robots and tape devices are tpautoconf and scan.  On Solaris platform the script sgscan can also be used.
These commands are located under the default "volmgr/bin" path:
 

Windows: C:\Program Files\Veritas\Volmgr\bin\
UNIX: /usr/openv/volmgr/bin/

How-to:
A) Scan and discover locally attached tape drives: tpautoconf -t
B) Scan and discover locally attached robotic devices (via SCSI and SAN): tpautoconf -r
C) Scan all locally attached devices: scan (or sgscan - Solaris only)
D) Scan and provide detailed robotic inquiry (for locally attached robot): scan -changer
For complete usage and additional switches, please review the NetBackup Command Guide:   http://entsupport.symantec.com/docs/340137 
NOTE: On UNIX/Linux, NetBackup commands discover devices by sending SCSI inquiries to all known SCSI devices via SCSI generic passthrough. If SCSI passthrough devices are not created or configured correctly, devices may be missing from the listing. NetBackup supplies passthrough drivers on Solaris (sg), and AIX (ovpass). For other UNIX/Linux, refer to Operating System support channel for passthrough driver support.