How you split millions of rows can be very different than shorter files, especially when you run into issues with file input/output issues in different language

How you split millions of rows can be very different than shorter files, especially when you run into issues with file input/output issues in different languages. Opening and working on an excel file with a few million rows can need a bit more ram than anticipated especially based on it's size/complexity. The quickest way I'd start with is to convert it to a CSV, read the file in, and rewrite it out 500 lines at a time.