[HELP] Standalone tape drive with backup Exec 2012

Hi all,

I'm implementing backup to tape with Backup Exec SP4. I use a LTO4 standadlone tape drive. When a runing backup job runs out of storage, I manually introduce a new tape but the new tape is rejected from the tape drive. Is there any preconfiguration tasks to the medias before it can be used by Backup Exec? How can I let backup exec spans its backups on two tapes?

thanks and regards,