Find which media tapes have the latest backup
                                                 Last update (2011-05-20 15:19:43)
                                                                                                                   Date added (2011-05-20 14:52:49)

Summary
You can find which media tapes have the latest RMAN backup with the following query:

SELECT RECID, STAMP, SET_STAMP, SET_COUNT, PIECE#, DEVICE_TYPE, HANDLE, MEDIA, 
STATUS, DELETED, START_TIME,  COMPLETION_TIME, BYTES
FROM GV$BACKUP_PIECE 
WHERE HANDLE LIKE '%ORACLE_ONLINE_SID%'
AND TRUNC(START_TIME) > TRUNC(SYSDATE-6) 
ORDER BY START_TIME DESC;

Where SID is the database SID, for example A7

To find the distinct tapes use:

SELECT DISTINCT(MEDIA) FROM GV$BACKUP_PIECE 
WHERE HANDLE LIKE 'ORACLE%A7%'
AND TRUNC(START_TIME) > TRUNC(SYSDATE-7);

MEDIA
-------------
VT1145
VT2059

Note: There are also and the archivelog backups (where HANDLE LIKE '%ORACLE_ARCHIVELOGS%' )