list backup summary

SELECT * FROM V$backup_piece where deleted='NO' 

 
SELECT COUN(*) FROM V$BACKUP_PIECE where DELETED='NO';
 

 237 

 
LIST BACKUP SUMMARY;
 

1900	792724610	1438	A	31/08/12	DISK	NO
1901	792735310	1439	A	31/08/12	SBT_TAPE	NO
1902	792735567	1440	A	31/08/12	SBT_TAPE	NO
1903	792735872	1441	A	31/08/12	SBT_TAPE	NO
1904	792735888	1442	A	31/08/12	SBT_TAPE	NO

RMAN> list backup summary completed between 'sysdate-41' and 'sysdate-40';

List of Backups
===============
Key     TY LV S Device Type Completion Time #Pieces #Copies Compressed Tag
------- -- -- - ----------- --------------- ------- ------- ---------- ---
1438    B  F  A DISK        31-AUG-12       1       1       NO         TAG20120831T011650
1440    B  F  A SBT_TAPE    31-AUG-12       1       1       NO         TAG20120831T041926
1442    B  F  A SBT_TAPE    31-AUG-12       1       1       NO         TAG20120831T042448

select count(*) from v$backup_set s, v$backup_piece p where s.set_stamp =p.set_stamp and deleted='NO' ;

237 rows 

is it normal that V$BACKUP_PIECE gives information about backups that are not marked DELETED (DELETED='NO')
but indeed, they are DELETED, i.e when we go to RMAN we don't find them ?

V$BACKUP_PIECE, what is it used for ?