RMAN-20261: ambiguous backup piece handle

While attempting to uncatalog backup piece :

RMAN> change backuppiece 'C:\INCREMENTAL\INC_J6PISCQS_1_1.BAK' uncatalog;

You could get an error :
RMAN-20261: ambiguous backup piece handle

In this case :

 Use the CROSSCHECK command to find the duplicate entries and delete them :

RMAN> crosscheck backup ;

RMAN> delete expired backup;

After this, you may continue to work.