Excerpt:
By configuring your system to run efficiently, you increase the amount of memory available to applications and ensure that they run smoothly. Increase the amount of memory available to Illustrator, quit applications you are not using, or disable nonessential startup applications or fonts to improve the performance of Illustrator.

Virtual memory

Virtual memory allows the system to use hard disk space to store information normally stored in RAM. Because it takes longer to access information on a hard disk than it does to access information in memory, using a portion of the hard disk as virtual memory can decrease performance.

Excerpt:
If you configure your system to run efficiently, then you increase the amount of memory available to applications and ensure that they run smoothly. Quit applications that you aren’t using or disable nonessential fonts to improve the performance of Illustrator.

Fonts

If you install only the fonts you need, then you will improve system performance and the performance of applications that access fonts. Each installed font increases the amount of RAM used by the system, which decreases the amount of RAM available to open applications and increases the amount of time applications take to display font menus. Use a font management utility, such as Extensis Suitcase, to help you manage a large number of fonts.