Format LTO Tape Backup Exec 2012

Hello, I hope you can help me ..

I have installed on Server 2008R2 Backup Exec 2012 with a DELL PowerVault 124T LTO has a magazine 8 tapes 800GB c / u. Because backup plans I have configured, can not find some method to format tapes, ie, I have several full tapes and want to use them again, I want to format the tape to use them again.

The most you have to do is delete the data but as Backup Exec says, the data is not deleted, but only disappear and others and the space remains the same, ie, full, just back a the option of inventory and catalog the data again appear and stay in them.

The model is Ultrium LTO4 tapes DELL

Server model DELL PowerVault 124T tape

I hope someone can help me ..

Thank you!