Autonomous Database has the ability to increase its storage or CPU cores. You can also activate auto scaling.

• Add CPU or Storage Resources or Enable Auto Scaling
  Describes how to scale your Autonomous Database on demand by adding CPU cores or storage. Also describes how to enable auto scaling.
• Remove CPU or Storage Resources or Disable Auto Scaling
  Describes how to scale your Autonomous Database on demand by removing CPU cores or storage. Also describes how to disable auto scaling.
• Use Auto Scaling
  When you create an Autonomous Database instance, by default compute auto scaling is enabled and storage auto scaling is disabled. You can manage auto scaling from the Oracle Cloud Infrastructure Console to enable or disable compute auto scaling or storage auto scaling.