RI for RDSoralce(BYOL)

Yes. For RDS Oracle (BYOL) platform, if you purcahse db.R5 reserved instance, it will be applicable to any active running db.R5 instance. For size-flexible platforms any RI of the same instance type, family & generation will be applicable to any running DB instance as long as DB platform is matching and they are in the same AWS region. So, you can apply db.r5.xlarge RI to db.r5.xlarge.tpc2.mem2x running RDS instance.

Non-size flexible instance types WILL NOT have normalization factor as a parameter. And size-flexible WILL. For example, in the case with latest generation mem-optimized instance classes, the normalization factor (NF) will be the same that corresponds to the size part:

• large = NF 4
• large.tpc1.mem2x = 4
• xlarge = 8
• xlarge.tpc2.mem4x = 8
• xlarge.tpc2.mem2x = 8
• 2xlarge = 16
• 2xlarge.tpc1.mem2x = 16
• 2xlarge.tpc2.mem4x = 16
• 2xlarge.tpc2.mem8x = 16
• and so on...

To confirm this, you can always check bulk API (pricing offer file): https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/using-ppslong.html

It contains info about pricing for all AWS services, all the combinations of possible features, usage types, API operations and regions. For example, for RDS, you can download pricing file in JSON format following this link: https://pricing.us-east-1.amazonaws.com/offers/v1.0/aws/AmazonRDS/current/index.json

I hope this helps :)