I have an array1 with 200k recs, array2 with 50K recs. Each array has the same amount of elements (170)...

You surely know what that means, but to me it doesn't seem to add up. Could you think that part of the problem over again and explain it in terms that someone who isn't already familiar with the problem would understand?

Once you've come up with an explanation that makes sense of that portion of your question, move on to the third sentence and find a way of clarifying what you mean there too.