Difference between encrypted backup of an encrypted DB and an unencrypted backup of an encrypted DB Let's say we have a fully encrypted database (the type of encryption is not considered in this scenario), and we produce two backups for that database.

If I encrypt only one of the backups, would there be a difference between it and the other one? Is it redundant to encrypt the backup if the database was already encrypted?

I ask from the perspective of the security of the data, not performance or anything else.

Thanks!
Does Rman Re-Encrypt TDE (Tablespace) Encrypted Data? (Doc ID 819167.1)

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  When using column encryption, these columns as well as other data in
  the tables are encrypted again during the backup. If you are using
  tablespace encryption these are not further encrypted during backups.


...


  ... for compressed backup on an encrypted tablespace, RMAN must decrypt
  all the blocks, compress them, and encrypt them using RMAN encryption ...