About Disk Caching

RAM caching is used in the viewports. You can also cache an operator's output to hard disk. The process of caching or committing an operator's output to disk is also called pre-rendering. Caching to disk frees RAM for other operators and/or more frames.

For example, if you are running out of RAM (as indicated in the status bar in the lower left corner), you can commit a few of the operators to disk. The RAM cache performance improves because less swapping is necessary.