System is running low on RAM. You may experience excessive parsing times and/or crashes. You will probably have to simplify the scene

This message appears on computers which are running out of available RAM during rendering. It is triggered by Windows reporting low free memory. Once memory runs out, 3ds Max might either crash, or start paging memory onto hard drive, resulting in extremely slow parsing and rendering.

In Corona Renderer 3 and newer, the "System is running low on RAM" error message will display a breakdown of various rendering components and their RAM usage. This provides the user with information what exactly should be optimized to lower the RAM usage. 

Possible causes and solutions:

  • Too high output resolution
    Solution: lower output resolution if possible
    Note: disabling the VFB may also help (Render setup > System > System Settings > VFB Settings > Type: none), however the memory saving may be negligible.

  • Too many render elements
    Solution: remove any unnecessary render elements, lower output resolution if possible

  • Denoising enabled for render elements
    Solution: enable denoising only for those render elements, where it is absolutely necessary

  • Too many high-resolution textures in the scene
    Solution: reduce the amount and resolution of bitmaps used in the scene

  • Displacement screen size value set too low
    Solution: do not use very high displacement settings unless it's absolutely necessary. Usually the screen size can be left at the default value. It should never be set to less than 1. Higher values mean lower quality. Always use autobump.

  • Using too detailed displacement maps
    Solution: use less detailed displacement maps. Let bump take care of fine detail. Autobump does that automatically.

  • Too heavy scene geometry
    Solution: optimize scene geometry if possible and reduce the amount of objects. Use instancing whenever possible. 

  • Computer has insufficient RAM installed to render the specific scene
    Solution: install more RAM (at least 64 GB is recommended for most "standard" interior and exterior scenes; 32 GB is the bare minimum)

  • Lots of memory-expensive applications running at the time of rendering
    Solution: close any other applications running on your computer that could take noticeable amount of memory (Such as Photoshop, Compositing software, web browser with many tabs opened, etc…)

Additionally "Low memory" option can be enabled in the Development/Experimental stuff rollout. This will slightly reduce RAM usage, but will also slow down rendering by about 5%. 

For other possible solutions, see: 

I am getting a sudden rise in RAM usage!