incremental backup does not creates 2 copies

Hi All,

when we create rman incremental backup with copies 2 option  , it is not creating 2 copies but when we take normal backup "backup copies 2 database" creates 2 copies.

Why it is?

RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT   '/u01/rmanbkps/%d_%s_%t_%p','/u03/rmanbkps/%d_%s_%t_%p';

old RMAN configuration parameters:
CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT   '/u01/rmanbkps/%d_%s_%t_%p';
new RMAN configuration parameters:
CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT   '/u01/rmanbkps/%d_%s_%t_%p',   '/u03/rmanbkps/%d_%s_%t_%p';
new RMAN configuration parameters are successfully stored

RMAN> backup copies 2 database tag='2copies';