About SCSI reserve operating system limitations on Windows
Windows operating systems cannot distinguish between a reserved device and a busy device. Therefore, PEND appears in the NetBackup Administration Console Device Monitor if another application controls the tape drive. NetBackup cannot share tape devices with other applications. If you use other applications, use the NetBackup tpreq command or Down the drive before using the drive.
These operating systems also may report PEND if the drive reports Busy when a volume is unmounted. Use the AVRD_PEND_DELAY entry in the vm.conf configuration file to filter out these extraneous reports.