Amazon RDS for Oracle now supports memory optimized R5b instance types for Bring Your Own License (BYOL) model, featuring up to 4x the RAM per vCPU of existing R5b instance classes to better fit your workloads. Many Oracle database workloads require high memory, storage, and I/O bandwidth but can safely reduce the number of vCPUs without impacting application performance. R5b memory optimized instances come in various configurations from 2 vCPU to 48 vCPU and memory from 32 GiB to 768 GiB and up to 32:1 memory-to-vCPU ratio. These configurations will allow you to right-size the Oracle workloads.
Source:: Amazon AWS