This counter tracks VOLUME OVERFLOW SCSI SENSE key errors on this LUN/flow, an error class again traditionally tied to sequential media (tape) where a command like a buffered write ran out of physical volume capacity before completing. An admin seeing this on a flow feeding a virtual tape or backup target should check whether the backup job's target media/volume was undersized for the amount of data being written in that job run. A backup job that grew unexpectedly large and overran its assigned virtual tape volume would generate exactly this error on the relevant flow.