Using Optimization settings, you can limit the virtual machine resource usage.
Note: The Optimization pane is available in Parallels Desktop for Mac Pro and Business Editions only. It is not available in the App Store edition of Parallels Desktop. For more information on the differences between the Standard and App Store editions, follow this link.
To access Optimization settings:
Do one of the following:
Click the Parallels Desktop icon in the menu bar and choose Configure.
If the Parallels Desktop menu bar is visible at the top of the screen, choose Actions > Configure.
Click Options and select Optimization.
If your Mac lacks resources for running two or more virtual machines at a time, you can manually allocate more resources to the machine that is more important for you. Drag the slider between Low, Medium, and No limit points. If you change this setting and don't like how Windows is performing, try a different setting.
