Thanks for letting me know about this. I'll revisit this code and look at different ways of accessing and importing the files. Are you running 64-bit Python? (the exe here is 32 bit) That alone may fix the issue if it is an error reading or writing beyond 2/4gb. I also had some sorting code that sanitized data that might be using big chunks of memory if it is still in play (haven't dug into this project for a while). If the csv file has 9gb of actual trade data and is not sparse, I would anticipate the sierrachart data files would also grow pretty large too.