How does Resolve acutally deal with GPU limitations?

In most applications I'm used to, having limited resources means that the application becomes slower and simply scales down resource usage. With Resolve, it seems like it simply gives up if it's out of VRAM. How does it actually work and why does it work that way?

It's one thing if that happens during color grading or editing, then I can work around it using proxy media and timeline proxy mode. The thing that confuses me is that I have this sneaking suspicion that VRAM requirements also apply during rendering, or at least it seems so when I work with projects that have a lot of things going on - render jobs often fail with vague errors. Is this unrelated or will Resolve also simply give up if it runs out of VRAM during export? Because if that's the case it sounds very limiting because proxy features can't even help you since you'll eventually have to render whatever you're working on.

Can someone shine some light on how Resolve actually deals with VRAM limitations in different scenarios?

My theory is a bug in how Resolve manages the resources of nVidia GPU's.

[Peter Chamberlain]

All image processing is in the GPU, so ur GPU needs sufficient spec to process the images based on the effects you apply.
Using proxy or optimized media allows lower performance systems to operate closer to or at real-time but doesn’t fix a fundamental lack of resources if the effects need more.

As an example, if u apply an effect that processes ok in HD, but uses all the resources of the GPU, the same effect and clip might simply not work at UHD res. There might just not be enough vram as an example fir those frames.

My theory is a bug in how Resolve manages the resources of nVidia GPU's.

Or a bug in CUDA, with AMD you don't have that problem.
Let's hope NVidia and/or BMD can give some clarity on this issue.

Or a bug in CUDA

Possibly, but that would suggest the issue would show up in other software as well, like Premiere Pro.

There might just not be enough vram as an example fir those frames.

The issue we're running into, Peter, is that VRAM often seems to get full even when it shouldn't. And the exact same project will process just fine on an AMD GPU with less VRAM.

So something is not working right with nVidia GPU's, and the issue has been there since Fusion was added.

Well, in my case I was probably actually just out of VRAM. GPU upgrade solved my issues and everything is fine.