In previous releases, the documentation on execution mode was buried in the Monitor Virtual Services page.
I decided to move the content to a standalone page in DevTest 10.0. You should now be able to find it more easily.
https://docops.ca.com/devtest-solutions/10-0/en/using/using-ca-service-virtualization/using-devtest-portal-with-ca-service-virtualization/monitor-virtual-services/execution-mode