Engine: [required] The database engine. RDS Custom for Oracle supports the following values:
custom-oracle-ee
custom-oracle-ee-cdb
custom-oracle-se2
custom-oracle-se2-cdb
EngineVersion: [required] The custom engine version (CEV) for your DB instance. This option is required for RDS Custom, but optional for Amazon RDS. The combination of Engine and EngineVersion is unique per customer per Amazon Web Services Region.