Problem definition
The Connecting JIRA applications to Oracle and Supported Platforms documentation does not explicitly mention if the Oracle 12c, 18c, 19c multitenant mode (or Container Database aka CDB) is supported or not and how to configure it.
Suggestion
Support the configuration and include the information above in the Supported Platforms and Database configuration documentation
This ticket is closed due to the fact that we don't support Oracle multitenant database.