Drives are active but does not show activity

I can give the output of nbrbutil -dump for one of the drives.You may get some idea .

firstuserid is empty . no job id but still I can see media is allocated. I have released those kind with nbrbutil -release swich. still they appear again and again

index=31 (Allocation: id={FBBD37D8-3FAA-11E6-9BAB-14F9893831A9} provider=DriveOperationProvider resourcename=DriveUnload masterserver=nyc-master.mycompany.loc groupid={00000000-0000-0000-0000-000000000000} userSequence=0 userid=""  firstuserid="" (Media_Drive_Allocation_Record: allocationKey=54033901 (Media_Drive_Record: MediaKey=4025436 MediaId=S24062 MediaServer=nyc-media02.mycompany.loc DriveKey=2000682 DriveName=16000 PrimaryPath=/dev/nst12 PoolName=Offsite_Linux RobotNum=1 RobotType=8 MediaTypeName=NetBackup HCART3 DriveTypeName=NetBackup HCART3 NdmpControlHost= RetentionLevel=0 PolicyType=2 JobType=15 MasterServer=nyc-master) (Storage_Unit_Record: STU= STUType=0 MasterServer= MediaServer= RobotType=0 RobotNumber=0 Density=0 OnDemandOnly=0 ConcurrentJobs=0 ActiveJobs=0 MaxMultiplexing=0 NdmpAttachHost= AbsolutePath=) (Bptm_Strings_Record: 0="MEDIADB 1 54033901 S24062 4025436 ------ 20 1467387069 0 0 0 0 0 0 10 22 0 16 1024 0 0 0" 1="VOLUME 1 S24062 4025436 S24062L6 ENCR_Offsite_Linux *NULL* *NULL* 24 8 1 15 0 {00000000-0000-0000-0000-000000000000} 0" 2="DRIVE 4 16000 2000682 82C6E9505B /dev/nst12 -1 -1 -1 -1 -1 -1 -1 -1 *NULL* *NULL* *NULL* *NULL* 1 0 0 1 0 0 /pci0000:00/0000:00:07.0/0000:06:00.1/host2/rport-2:0-12/target2:0:12/2:0:12:" 3="STORAGE 1 *NULL* 0 0 0 0 0 0 nyc-media02.mycompany.loc nyc-media02.mycompany.loc *NULL*" 4="DISKGROUP 0 6 *NULL* 6 *NULL* 6 *NULL*" 5="DISKVOLUME 0 6 *NULL* 6 *NULL* 0" 6="DISKMOUNTPOINT 0 6 *NULL*" ) TpReqFileName=))

        MdsAllocation: allocationKey=54033901 jobType=15 mediaKey=4025436 mediaId=S24062 driveKey=2000682 driveName=16000 drivePath=/dev/nst12 stuName= masterServerName=nyc-master mediaServerName=nyc-media02.mycompany.loc ndmpTapeServerName= diskVolumeKey=0 mountKey=0 linkKey=0 fatPipeKey=0 scsiResType=1 serverStateFlags=3