swap memory heavy load solution?

If DaVinci Resolve was showing “Not Responding” while using about 6.36 GB of memory, that number by itself does not mean Resolve was using too much RAM.

The same applies to the swap file you noticed. 

macOS routinely uses virtual memory and can move some data between RAM and the Mac's startup disk when needed. 

Swap Used in Activity Monitor simply tells you how much storage is currently being used for that purpose. 

Having some swap does not, by itself, mean there is a problem. (Apple — View memory usage in Activity Monitor)

This also helps explain why the problem could appear today even though you have been editing the same project for 15 days. 

The memory demands are not necessarily the same throughout a project or from one moment to the next. 

You may have reached a more demanding section of the timeline, added effects or other processing, had more applications running, or simply reached a point where the workload temporarily required more resources. 

That does not mean you necessarily did anything wrong.

The key thing to look at is Memory Pressure, rather than simply seeing that swap exists. 

Apple says Memory Pressure reflects how efficiently your Mac is handling memory and takes things such as available memory, compressed memory, cached files, wired memory, and the rate of swapping into account. 

If Memory Pressure was high when Resolve stopped responding, memory pressure could have been a contributing factor. 

If it remained green, memory would be less likely to be the main cause. (Apple — View memory usage in Activity Monitor)

Your 4K footage and slow hard drive are also worth considering. 

The external drive does not cause macOS to use swap, but a slow drive can make it harder for Resolve to read and write large video files quickly. 

If the drive was heavily occupied at the same time as memory, CPU, or GPU resources were under pressure, that could contribute to Resolve becoming unresponsive.

I would not try to disable or manually remove the swap files. 

They’ are part of normal macOS memory management. Instead, we should find out which resource was actually under pressure when the freeze occurred. 

Activity Monitor's Memory, CPU, and Disk information can help distinguish a memory problem from a storage, processor, or Resolve-specific problem. (Apple — Activity Monitor User Guide)

So, based on what we know so far, there is ’no reason to assume you did something wrong. 

The fact that this happened today rather than during the previous 15 days does not, by itself, tell us what caused it. 

The Activity Monitor readings from around the time of the freeze should give us the answer.

That screen shot is nearly impossible to read, but it looks like you are trying to do video editing on a system that has 16 GB of real memory. Swap used is 19.81 GB, and the Memory Pressure graph is all Yellow.

Clearly macOS believes that the amount of RAM that you have is marginal for the workload that you are dumping on it, and the huge swap figure would certainly suggest that performance might be in the Yellow or Red area.

Of your physical RAM, 6.48 GB was holding "Compressed" data – another form of swap. (The theory here is that a modern CPU is fast enough that swapping out a page of memory to a compressed area of memory – burning CPU cycles in the process – is probably faster than waiting to flush data to a disk, or read data from a disk. But obviously there is only so much compression that you can do before you are forced to go swap to the disk.)

If the load was this heavy today, and not days before, that might suggest that you are running some application that is leaking memory, and that occasionally restarting the application, or even restarting the Mac, might help.

However, 16 GB of RAM seems kind of on the low side for a machine whose main job is doing editing of big 4K video files.

daVinci is likely not responding because it is calling VTDecoderXPCServices which is using up all the RAM and swap (and likely CPU) and daVinci is not responding because that service it called upon hasn't completed.

It may be possible in daVinci settings to limit RAM usage. I know on a couple photography apps that I use they have the option to set a max memory usage. There may be such a setting in daVinci assuming that also controls memory used up by the service it is calling.

So, as your set up is now, you are pushing the 16GB RAM in your machine to the limit and therefore may not be really suited to the task you are demanding of it.

...i have been editing for more than 15 days

The occasional restart clears Swap