Legato Networker on AIX

We have one legato networker for AIX version 6.1 installation. Here we are configuring the backup policies and in one of the backup policies, we have to have overwrite option. i.e today there will be a full backup on one tape and the same tape has to be overwritten after one week.

But i am not able to configure overwrite option, instead it is appending to the old backup.

Can some body help me in configuring with overwrite option without relabelling the tape.

Thanks & Regards,

chandra