Just for reference: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4480364878.html suggests an upper limit on governance and a 50 MB data limit. I'm not an expert at hacking NS M/R yet, but it seems to be pretty good about splitting (done for you at the end of getInputData()) and shuffling (done for you at the end of Map()) your data. If you are using N/search and can search.runPaged() you should be able to split up even huge data sets across multiple M/R runs by passing in different pages into getInputData(). Theoretically, it should work, but I've still yet to try this.