I was thinking more about performance than space. If you hit the disk for every recursive call (not sure if it is the case, I can't read COBOL) the performance

I was thinking more about performance than space. If you hit the disk for every recursive call (not sure if it is the case, I can't read COBOL) the performance is probably going to be terrible even if the files are memory mapped. Optimized tail recursion would avoid most of that.