Sometimes when I make a heavy scene, while the graphics card can handle it, and I can get fine GPU viewport rendering, hitting F12 will see all my RAM getting used up and I have to shut down my PC.
Can’t tell you how much time this loses me on jobs. Any possible way to get Blender to just not do that besides the obvious of spending ages making all my textures low res until it stops happening. I’d rather Blender just tell me my scene is too large.
No, it’s not possible and it’s a real problem with Blender that not many seem to be interested in discussing how to solve.
There are very many situations where RAM quickly starts to fill up leaving the user no chance to stop the process before Blender get an unresponsive GUI or Blender/System Crash.
For example when the interface of Blender gets slow/laggy due to some heavy scene, and you have to enter a value in some field, and due to the slow interface response you enter a wrong value and hit Enter. Just as one of many examples, entering 0.0 value in Remesh (Voxel) modifier (Don’t try this without having a quick way to kill Blender process handy)
Gah, such a shame. I’m so close to just reverting back to other 3d software because Blender is SO slow and crashy. And I know exactly what you mean about the remesh thing. Same if you accidentally drag the slider. I get sick of seeing all these youtube videos like “wow, new features in 3.xxx” and I’m just thinking, yeah but is it still a crash beast with no lock icon on the render dimensions?
How much RAM do you have?
Buy more RAM? 
Blender does not know how much there is available VRAM. You may have other graphic applications open, accelerated desktop and so on.
What you can do is to estimate your ram usage when planning your scene.
One channel 4K texture = 16Mb
4K HDR 200Mb
8000000 vertex = ~1Gb
Just fit everything your VRAM to keep things fast. Using more cause slowdown or out of memory.
CPU compute will take longer but won’t crash. GPU is crashing because can’t swap. With your status bar enabled (Windows > Show Status Bar) you can check how much VRAM is being used, if it’s near cap avoid GPU compute. CPU is slower (considering you don’t have a Threadripper or a high end Epyc) but stable.
You will find that other DCCs respond in kind when overtaxing your hardware.
In my experience Blender actually deals pretty well with heavy scenes compared… Some of the commercial brethren do far worse.
Any 3d software can be easily brought down to its knees with excessive values/objects/geometry/textures/etc. I do agree it would be nice if 3d software would warn the user about curbing their expectations when they set an unrealistic sky-high value in their array modifier, or use dozens of 16K textures on a 16GB machine. But in the end it really is the responsibility of the artist to know your software’s and hardware’s limits. And learning about ways to work around these. This is part of “the job” of any designer.
@wonderland78 It would be useful if you shared your system specs with us.
well, I have 32gb on my laptop and when I use that while travelling, it’s obviously worse than my home PC which has 64gb. But I can still have that happen on the PC, just less often.
I did have it crash with CPU render as well. I thought of that but alas it crashed.
It’s almost irrelevant what my spec is. I have two machines I use, one has 32gb and a gtx 1070, and the other has 64gb with an rtx 3060. It’ll smash them both but obviously the laptop is far worse.
I’ve already maxed out both machines.
What kinds of scenes are you making? 32GB (and 64) should be more than enough for most applications. I too have 32gb and a 1070, and normally it’s my GPU that bottlenecks when rendering, as it only has 8gb of VRAM and Blender will eat that up quite quickly, depending on what I’m doing. Normally though, I only max out when rendering a scene with lots of 4k+ textures, hair particles, etc…
I have made it a habbit to allways have the task manager open when i start rendering a new scene where I am not familiar with the RAM usage yet. That way if the RAM or VRAM reaches a critical point I can kill the process.
You have 128GB on both machines?? That’s impressive, wow. I’m jealous
You may have different (viewport/render) levels of subdivision in your objects, that will greatly increase RAM usage.
in this time and age it is “features over performance”.
Use something like Process Tamer or Process Lasso and set it up to kill Blender if it uses more than X amount of memory. Then, you just have to remember to save before doing anything that could use too much memory and get it killed. PowerSave is a nice addon for doing this automatically.
yeah coz all computers have 128gb as their max capacity. Muppet.
I think those programs only kill CPU usage. Might be wrong.