Final answer:
The Oracle Autonomous Database by default performs automated database tuning, automated backups, and automatic patching to ensure high availability and optimize performance.
Step-by-step explanation:
The Oracle Autonomous Database performs several tasks by default to provide a fully managed service experience. One key task that is performed by default is the automated database tuning process. This includes automatic optimization of database performance through tasks such as SQL query optimization, resource allocation, and automatic indexing. Another major default task is automated backups, where the database automatically performs backups to protect against data loss. Lastly, the database ensures high availability through tasks like automatic patching, which applies security updates and bug fixes without manual intervention.