Rman backup media timing

Hi,

We are doing RMAN backup to disk and also TSM using TDPO agent.

1. (disk)
BACKUP DEVICE TYPE DISK INCREMENTAL LEVEL 1 FOR RECOVER OF COPY DATABASE tag='FULL_WEEKLY';

and then to TSM

2. (TSM)
BACKUP DEVICE TYPE SBT_TAPE tag='FULL_WEEKLY' RECOVERY AREA;

I can get all required info from rc_backup_status i.e. start /end /status backup
I also need to have this info about TSM backup. I can see data about media backup in rc_backup_pieces but I am not sure how to link it with c_backup_status.

It would be great if someone could give me a clue ! Thanks