How to get the relationship between backup set? We use command backup database to perform a full backup, serval backup sets are generated during the backup operation.
Also, we use list backup to show the backup information, the output as followed:

BS Key  Size       Device Type Elapsed Time Completion Time
------- ---------- ----------- ------------ ---------------
7       136M       DISK        00:00:20     04-NOV-06      
        BP Key: 7   Status: AVAILABLE  Compressed: NO  Tag: TAG20071104T200759
        Piece Name: /d2/RDBMS/backupset/2007_11_04/o1_mf_annnn_TAG20071104T200759_ztjxx3k8_.bkp

  List of Archived Logs in backup set 7
  Thrd Seq     Low SCN    Low Time  Next SCN   Next Time
  ---- ------- ---------- --------- ---------- ---------
  1    1       173832     21-OCT-06 174750     21-OCT-06
  1    2       174750     21-OCT-06 174755     21-OCT-06
  1    3       174755     21-OCT-06 174758     21-OCT-06

BS Key  Type LV Size       Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
8       Full    2M         DISK        00:00:01     04-NOV-06      
        BP Key: 8   Status: AVAILABLE  Compressed: NO  Tag: TAG20071104T200829
        Piece Name: /disk1/oracle/dbs/c-774627068-20071104-01
  Controlfile Included: Ckp SCN: 631510       Ckp time: 04-NOV-06
  SPFILE Included: Modification time: 21-OCT-06


From above output, I could not figure out whether such backup sets are generated by the same command, backup database. Is there any available command to satisfy my requirement?
From SQL:

SELECT p.start_time, p.handle, p.tag, s.backup_type, 
       s.incremental_level, controlfile_included
FROM   v$backup_piece p, v$backup_set s
WHERE  p.set_stamp = s.set_stamp
AND    p.set_count = s.set_count
ORDER BY tag;


For the backup type: 

L: Archived Redo Logs
D: Datafile Full Backup (or control file backup or autobackup)
I: Incremental Backup 


You can see which files are in each backup by the TAG column.  

Keep in mind that this view may report backups are don't actually exist on disk unless you:

RMAN&gt; crosscheck backup;
RMAN&gt; delete expired backup;


Refer to the Oracle Database 12c Documentation (or whatever version of Oracle you are using) for more information: 

v$backup_set

v$backup_piece