BACKUP ... FORMAT '%P'
Oracle documentation mentions that '%P' spicifies the backup piece within the backupset. See link below:
http://docs.oracle.com/cd/E11882_01/backup.112/e10643/rcmsubcl010.htm#i82206
"Specifies the piece number within the backup set. This value starts at 1
for each backup set and is incremented by 1 as each backup piece is created"
So in my RMAN I use backup command.
backup as backupset format 'bks_%d_%p_%t.bk' database;
and under OH\database I get the files:
BKS_DHMAN_1_797111122.BK
BKS_DHMAN_1_797111107.BK
According to documentation one of the 2 should be
BKS_DHMAN_2_.....BK