error join two data sets

I started a coursera course on genomics and the first assignment is to work with datasets. I am joining two datasets and i am getting the error data file has frown too big showing is around 200 Gb after many hours of processing the 2 data sets that are small files.
I have already refreshed the page, deleted the history and started a new history.
Any advice on how to solve this, please?
Thank you