I am now an Oracle Cloud Infrastructure 2019 Certified Architect Professional, thank you Oracle for free 6 OCI exams until 15th May.
A good documentation source to understand the Oracle Cloud Infrastructure concepts and a good materials to prepare for Oracle Cloud Infrastructure certifications
Introduction to Oracle Cloud Infrastructure: (level 50):
Explore level 50 training content to start your journey on Oracle Cloud Infrastructure. The learning material will cover an introduction to Oracle Cloud Infrastructure, its architecture and various services.
Core Infrastructure (level 100):
Oracle Cloud Infrastructure Level 100 videos teach you the basics of each of service and establish a grounding for more advanced concepts.
Core Infrastructure (level 200):
Find Level 200 deep dive training content on Oracle Cloud Infrastructure services. It includes training content on following sections: core infrastructure, solutions-platform-edge, database, governance and administration.
Cloud Migration (level 300):
Explore level 300 training content that covers solutions on Oracle Cloud Infrastructure. The learning material will cover advanced topics like data migration, reliability and resiliency, Exadata cloud service, and Oracle applications.
Good Luck !!