Y'know, one of my thoughts/questions as I see this thread developing is this:
The original question's title is this: "How to test if data was successfully copied" and the original question is "how do we test db load".
It appears that we immediately went to "performance testing" by virtue of seeing the word "load" in the original question. But, I have the sneaking suspicion that the real question is (or should be): how do we validate data loaded to a database correctly? (or something not too distant from there.)
But, like Peter asked and stated, we need more detail to really know for certain how to address the original question.
"The single biggest problem in communication is the illusion that it has taken place."
-George Bernard Shaw, Irish playwright and Nobel Prize winner, 1856-1950