Difference between OPM RPG and ILE RPG

There are a few areas where the ILE RPG compiler runs faster because of the
way the compiler and runtime are coded. For example, the handling of eof
and record-not-found is much faster for ILE RPG. Also, program
initialization is much faster when you have no PSDS or a small PSDS (this is
most dramatic when the called program returns immediately).

There may be some difference due to the fact that the ILE RPG runtime is
statically bound and the OPM runtime is not, but this may not be as big a
difference as you'd expect, because the OPM RPG runtime is used much less
than the ILE RPG runtime. Many OPM RPG programs only call the
initialization runtime program; all the code is generated directly into the
program rather than calling out to the runtime; system programs for file
handling are called directly from the generated code.

I think most of the difference is due to the optimizating translator used by
the ILE compilers, which takes the code generated by the compiler and
generates machine code.