"unable to decrypt backup"
*Cause: A backup piece could not be decrypted. This message is accompanied
with another message that indicates the name of the encrypted
backup that could not be restored. The reason could be either
that an invalid password was entered, or that, when using
transparent decryption, the database external security device
is not open.
*Action: If password-based restore was enabled for this backup,
then supply the correct password using the RMAN SET DECRYPTION
command. If transparent restore was enabled for this backup,
then ensure that the database external security device is open.