This was fixed in JDK 11 (amongst other changes) with JDK-8194814. That change bumped the default MaxRAM value for ppc64le from 4GB to 128 GB. This is an 8u-specific bug for fixing the MaxRAM default in isolation, rather than backport the other changes in order to reduce risk.

When MaxRAM has not been set explicitly by the user via a JVM flag, the default value acts as a ceiling for the total available heap memory. Settings such as MaxRAMPercentage will be calculated against this ceiling of 4GiB, preventing larger heaps. We have had customers try to set higher limits (via the container subsystem) and not understand why the JVM did not size itself to those larger limits. The change aligns the MaxRAM default value with the other 64-bit ports.