Beware: Oracle RMAN Password Only Encrypted Compressed Backups to Tape Might Not Decrypt

So, a few weekends ago I had a BIG scare. I was moving an Oracle Database Appliance from one data center to another. Oracle said the only supported method to do so was to wipe the machine back to bare metal and rebuild it in the new data center with all the new IP addresses and network settings. To prepare for this I did a cold backup of a database to tape (really Oracle Cloud Backup) and used the following RMAN commands:

RMAN> set encryption on identified by ******************* only;
RMAN> backup device type sbt incremental level 0
      tag '2018_06_29_SERVER_MOVE' force as compressed backupset database;

Unfortunately, when it came time to read that backup from Oracle Cloud Backup (our configured sbt device), I got the following error:

ORA-19913: unable to decrypt backup

As I worked through the issue with Oracle Support for a very long time I eventually started working with some support folks who said the following:

“I’ve seen issues in the past when you do a password only encrypted compressed backup to tape where it can’t be decrypted. You shouldn’t do that.”

I think this is potentially one of the biggest bugs in the history of Oracle (if you can’t trust a backup then something is very very wrong!) if the issue is really there… I’ve yet to be able to do any additional testing of this, but figured I’d give folks a warning.

As an aside, I did take a disk backup before the tape backup and then copied the disk backup to a mounted NFS drive. I was able to move that disk backup over to the server and restore from it, so no customer data was harmed during the server move.