I'm currently using a 10% sample of a very large dataset (10 vars, over 300m rows) which amounts to over 200 GB of data when stored in .dta format for the full dataset. Stata is able to handle operations like egen, collapse, merging, etc in a reasonable amount of time for the 10% sample when using Stata-MP on a UNIX server with ~50G of RAM and multiple cores. I'm currently using a 10% sample of a very larg