Java on the AS/400 is the weirdest thing. The whole platform was designed to be compile once to near assembly and then run cached byte code or whatever. Java is just too late compilation is clunky in comparison imo.
I believe Tribes 2 did something similar just at a higher level
TIMI is compiled at installation time usually, the bytecode format is used only as portable executable format.
While initially Java on AS/400 did take advantage of TIMI, IBM eventually moved away from it, into regular JVM design on now IBM i.
Most likely because IBM z doesn't use TIMI, rather language environments, and they want a more straight design, or due to Java dynamic capabilities using TIMI wasn't the best approach.
On AS/400 (IBM i), only Metal C, and the underlying kernel/firmware, written in a mix of PL.8, Modula-2 and C++, are pure native code.
Smalltalk was OS/2's .NET, so to speak.
Unfortunately it all died alongside OS/2, followed by IBM's pivot to Java.