Description
"Pause virtual machine when no applications are running" feature is designed to save your Mac resources. Pausing a virtual machine releases the resources, such as RAM and CPU, currently used by this virtual machine. The released resources can then be used by the host computer and its applications or by other virtual machines running on the host computer. If you select this option, the virtual machine will be automatically paused provided that:
- the virtual machine is running but the virtual machine window is not active over 30 seconds
- there are no applications running in the guest operating system (no icons of the guest OS applications are present in the Dock)
Virtual Machine Configuration -> Options -> Shared Applications -> Pause virtual machine when no applications are running

Note: These options are available only when Parallels Tools are installed in the virtual machine and the Isolate Mac from Windows option disabled in the Security pane