You will likely be unaware of your Mac’s virtual memory (VM) until you find that its performance has slowed to a crawl. This is a temporary memory reserve, from which a Mac’s Random Access Memory (RAM) borrows to perform operations. RAM is fast physical memory. VM is much slower swappable memory, located on a disk drive. When needed, a Mac will dynamically allocate additional virtual memory, and you can do little to tune VM allocation. However, keep in mind that a Mac uses free disk space as virtual memory, so a full boot disk can cause problems. Writer Bio
