Investor/RT for Windows has a built-in warning system designed to alert you if memory usage climbs to abnormal levels.
This system was designed for past versions of Investor/RT (until IRT 14), which were 32 bit applications. Current Investor/RT versions (15 and higher) are 64 bit and such memory limitations are no more valid
Reminder : Investor/RT (version 14 and older) are 32 bit application and the max memory usage for a 32-bit application is around 3.5 GB. You will get a warning if memory usage exceeds 1024MB (around 1 GB). Most users run substantially under that (usually by about half). If you routinely recieve a warning message because you have an unusually demanding Layout, you may revise the warning threshold to a higher level by going to File > Preferences > Configuration and using the "Find" box to search for the Configuration Variable called MemoryUsageWarningMB. Then set this value to something higher such as 1500.