Overwrite a file using dbmcli command

Hi  Experts,

                        I have create a backup medium using dbmcli command :

dbmcli SIT>medium_put DATA /backup_disk/SIT/DAT0001 FILE DATA

dbmcli SIT>backup_start DATA

I am able to take backup successfully.

I would like to know the command which overwrite the already existed  backup file.

Please help..

Thanks

Srikanth