我该如何理解app bundle中的tmp文件夹？它会在某个时刻被清除吗？

I'm capturing video using my app. I was thinking about saving the captured movie to Documents folder. I've explored project bundle and saw the captured movie is saved 2times. It's in tmp and also in my Documents folder. Will tmp folder be cleared or something? Or it's ok to keep the captured movie only in tmp? Thanks in advance.I'm capturing video using my app. I was thinkin