This warning message is caused by selecting too much hourly or sub-hourly data. In cases where there is too much data DesignBuilder will often crash following the message. The cause is usually an annual simulation with hourly or sub-hourly results requested in a medium to large sized model. The only solution in this case is to reduce the amount of data generated or the simulation period.

Fitting extra physical memory will not help as there are limits to the amount of simulation data that can be read into DesignBuilder.

If you really need hourly or sub-hourly results for the whole year then you should restrict the results to be only for certain zones, surfaces etc. This can be done using the Options model data tab.

Alternatively use the Results Viewer application for viewing large amounts of hourly/sub-hourly data as this is does not suffer from the same problems. You can ensure that DesignBuilder doesn't read simulation results (and run the risk of crashing) by unchecking the “Auto load ESO” option on the EnergyPlus tab of Program options as explained at:

http://www.designbuilder.co.uk/helpv3.4/#_Program_options_Calculations.htm

For more tips on working with large models: http://support.designbuilder.co.uk/index.php?/Knowledgebase/Article/View/26/0/working-with-large-models-and-speeding-up-simulations