The Nazis utilised the best information-management tools of the time, including IBM computers (fully supported by IBM throughout the war) and punch cards (as another commenter notes: <https://news.ycombinator.com/item?id=42359352>). Those tattoos worn by concentration camp survivors were IBM-assigned identifiers.

Nazis also used census and other civil data sources. Deliberate destruction of such records in the Netherlands is one of the legacies of WWII:

<https://en.wikipedia.org/wiki/The_Holocaust_in_the_Netherlan...>

This and other legacies of 20th-century genocide are chief reasons why European attitudes toward rampant data collection and exchange are far harsher than in the United States. Though I'd argue still not nearly harsh enough.