If you say that increasing the heap doesn't help are we talking about decent sizes like 8GB+? Also did you increase the java opts AND the container size? set hive.tez.java.opts="-Xmx3400m"; set hive.tez.container.size = 4096; If yes then you most likely have a different problem like for example loading data into a partitioned table. ORC writers keep one buffer open for every output file. So if you load badly to a partitioned table they will keep a lot of memory open. There are ways around it like optimized sorted load or the distribute by keyword. http://www.slideshare.net/BenjaminLeonhardi/hive-loading-data If however you use significantly less than 4-8GB for the task then you should increase that. ... View more