callnat with long list of parameters

Any statistics of callnat performance with long parameters (thousands of fields?)

Basically, performance degrades as the number of parameters increases. To be quite honest, i would have to check the manual to see if there is an upper bound on the number of parameters for a subprogram. “thousands” seems a bit unlikely; hundreds would certainly degrade performance quite a bit.

More commonly, you would pass a single large field that has been REDEFINE’d ;
for example

             1 #DATA (A500)
             1 REDEFINE #DATA
                2 #A1 (A10)
                2 #A100 (A3)

              CALLNAT 'MYSUB' #DATA

and MYSUB would have a Parameter Data Area with #DATA REDEFINE’d as above