Explanation
DATA ENCRYPTION
Protect customer data at-rest and in-transit in a way that allows customers to meet their security and compliance requirements for cryptographic algorithms and key management The Oracle Cloud Infrastructure Block Volume service always encrypts all block volumes, boot volumes, and volume backups at rest by using the Advanced Encryption Standard (AES) algorithm with 256-bit encryption.
By default all volumes and their backups are encrypted using the Oracle-provided encryption keys. Each time a volume is cloned or restored from a backup the volume is assigned a new unique encryption key.
The File Storage service encrypts all file system and snapshot data at rest. By default all file systems are encrypted using Oracle-managed encryption keys. You have the option to encrypt all of your file systems using the keys that you own and manage using the Vault service.
Object Storage employs 256-bit Advanced Encryption Standard (AES-256) to encrypt object data on the server. Each object is encrypted with its own data encryption key. Data encryption keys are always encrypted with a master encryption key that is assigned to the bucket. Encryption is enabled by default and cannot be turned off. By default, Oracle manages the master encryption key.

Explanation
Oracle offers several different service level agreements as defined in this section (Service Level Agreements).Service level agreements range from least restrictive (data plane) to more restrictive (control plane) to most restrictive (performance).

Explanation/Reference: https://www.oracle.com/assets/paas-iaas-pub-cld-srvs-pillar-4021422.pdf