Thanks for this answer.
You stated: "I don't see why you talk about 20 000 000 combinations, CREATE should not created that many combinations, at least if only Account, Customer are contained in the one and only relation."
The reason that I talk about 20.000.000 combinations is that in the debugger at the end of CREATE E_TH_CHAS contains the expected number of valid combinations (500*100=50.000), BUT the applicaiton interrupts with RSPLS_CR 027 and the accompanying message indicating that millions of combinations is due to be generated by the current parametrization.
Please note: E_TH_CHAS contains only the IOBJs Account and Customer and CREATE is only called once.
As I mentioned above: CREATE is not always called, but when it is the application always interrupts as described.
I have not yet been able to locate the setting you mentioned in "1 Remark", but irrespectively of that it seems to me as if the system is not behaving the way you describe that it should.
Do you suggest that I open an incident?
Note: we are not using 'external buffering'.