Stop a running SQL query quickly

This applies to embedded and dynamic SQL queries in Caché ObjectScript. If I attempt to terminate the process via Management Portal, nothing happens. Neither does Ctrl C nor closing the terminal window in which my program is running, nor setting a stop flag in a global which is read by the program on each loop iteration. The only way to stop the query appears to be restarting the Caché server (which is running locally on my PC).