The Oracle version 19.0.0.0 is not supported. The supported versions are 12.1.0, 12.2.0.
This message is correct for RSA Identity Governance & Lifecycle version 7.1.1 and earlier.
This is a known issue in RSA Identity Governance & Lifecycle 7.2.0 and 7.2.1 versions. Certification of Oracle Database 19c for RSA Identity Governance & Lifecycle 7.2.0 and 7.2.1 was completed AFTER the release of these versions. Oracle 19c is supported on these versions but the warning level message will be shown until you upgrade or patch to the version where this issue is resolved.