Hi The, It eventually turned out that I did not need that much memory, because the line "cluster _psu;" was to be removed. Plus, I got a funding to purchase a laptop with large RAM and fast CPU. Since then, I haven't encountered many problems... BTW, do you also use the BRFSS data? If so, you may not really need cluster, because each cluster includes only one record, as far as I have checked. Hope this help. Rakkoo
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