If you do not have barcode labels, then you need to inventory your library to update the tape status to BE. You either right-click on the library to inventory the entire library or right-click on a particular slot and right-click to inventory the slot.
It is more efficient to use barcode labels, you can then forget about inventory and just do scans. See my article below on how to do your own barcode labels.
https://www-secure.symantec.com/connect/articles/using-barcode-labels-why-and-how
