For general guidance on methods and tools to migrate databases to Oracle Cloud Infrastructure database services, including Exadata Cloud Infrastructure see "Migrating Databases to the Cloud".
A recommended approach for migrating to Exadata Cloud Infrastructure is using Zero Downtime Migration
Moving to Oracle Cloud Using Zero Downtime Migration
Oracle now offers the Zero Downtime Migration service, a quick and easy way to move on-premises databases to Oracle Cloud Infrastructure.
Zero Downtime Migration leverages Oracle Active Data Guard to create a standby instance of your database in an Oracle Cloud Infrastructure system. You switch over only when you are ready, and your source database remains available as a standby. Use the Zero Downtime Migration service to migrate databases individually or at the fleet level. See Move to Oracle Cloud Using Zero Downtime Migration for more information.