SSI function code 4 is similar to SSI function code 50 (Early End-of-Task call). The only difference is that, for SSI function code 4, your routine is given control after most resource managers are given control. For SSI function code 50, your routine is given control before most resource managers are given control. If you want to obtain control before most resource managers have been invoked, see SSI function code 50 (Early End-of Task).