nbrbutil -dump
This is NOT easy to read, but will do what you want.
root@womble $ nbrbutil -dump |grep advanced_disk_sp3 |grep index
index=3 (Allocation: id={0FE5F198-CC1C-11E1-A51E-00144F58313C} provider=MPXProvider resourcename=advanced_disk_sp3 masterserver=womble groupid={100510B4-CC1C-11E1-B7B0-00144F58313C} userSequence=0 userid="jobid=185" firstuserid="jobid=185" (Media_Drive_Allocation_Record: allocationKey=106 (Media_Drive_Record: MediaKey=0 MediaId=@aaaah MediaServer=womble DriveKey=0 DriveName= PrimaryPath= PoolName= RobotNum=0 RobotType=0 MediaTypeName= DriveTypeName= NdmpControlHost= RetentionLevel=0 PolicyType=2 JobType=1 MasterServer=womble) (Storage_Unit_Record: STU=advanced_disk_sp3 STUType=0 MasterServer=womble MediaServer=womble RobotType=0 RobotNumber=-1 Density=0 OnDemandOnly=1 ConcurrentJobs=2 ActiveJobs=0 MaxMultiplexing=1 NdmpAttachHost= AbsolutePath=/sp3) (Bptm_Strings_Record: 0="MEDIADB 1 106 *NULL* 0 *NULL* 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0" 1="VOLUME 1 *NULL* 0 *NULL* *NULL* *NULL* *NULL* 0 0 0 0 0 {00000000-0000-0000-0000-000000000000} 0" 2="DRIVE 3 *NULL* 0 *NULL* *NULL* 0 0 0 0 0 0 0 0 *NULL* *NULL* *NULL* *NULL* 0 0 0 1 0 0" 3="STORAGE 1 advanced_disk_sp3 0 524288 0 6 0 0 womble womble *NULL*" 4="DISKGROUP 0 12 AdvancedDisk 6 womble 20 Advance_DiskPool_sp3" 5="DISKVOLUME 0 6 @aaaah 4 /sp3 0" 6="DISKMOUNTPOINT 0 4 /sp3" ) TpReqFileName=)))
In that lot above, the jobid and media are listed.
In this example the job id is disk, but it would work for tape media as well.
Opening the details in the [program textpad, displays it as one long line, one line per jobid.
So, then , count the lines ...
Regards,
martin