Retain the terminated database backups and lock the ACD backup retention period

Autonomous Database on Dedicated Exadata Infrastructure does not delete the database backups upon terminating any (or all) of the Autonomous Database components, like Exadata Infrastructure, Autonomous VM Cluster (AVMC), ACD, and Autonomous Database. You can enable the backup retention lock to prevent any unwanted deletion of the ACD backups and long-term backups before their retention period after an ACD is terminated.

See About Backup and Recovery for more details.