The compute engine and database server have a timeout mechanism that causes them to exit if no requests have been made of them for a certain period of time so they do not run indefinitely if their connection to VisIt's viewer is severed. You can set this period of time, or timeout, by typing in a new number of minutes into the Timeout text field. You can also increase or decrease the timeout by clicking on the up and down arrows next to the Timeout text field.