PEND-robot_designation (Applies only to robotic drives)
For example, PEND-TLD.
PEND (Applies only to standalone drives)
If the drive reports a SCSI RESERVATION CONFLICT status, this column shows PEND. This status means that the drive is reserved when it should not be reserved.
Some server operating systems (Windows and HP-UX) may report PEND if the drive reports Busy when opened. You can use the AVRD_PEND_DELAY entry in the Media Manager configuration file to filter out these reports.
I would verify that all your media servers have SSO and are set up as SSO for all the drives.
You might take NB down on the media servers and bring it up one at a time to see if one of the media servers is causing the issue.