Powering up the system consists of two steps: physically switching on the central processing unit (CPU) and performing an Initial Program Load (IPL). The system needs you to perform an IPL periodically because it is the only time the operating system performs certain essential "housekeeping" tasks. It's recommended that you plan a periodic IPL schedule. However, if your organization must have the system up and running 24 hours a day, 7 days a week, recent improvements in the operating system allow you forgo periodic IPLs. As shown in Chapter 7, Operational Assistant can simplify the task of scheduling an IPL. Two basic types of IPL are available: unattended and attended. A third type, remote IPL, isn't described in this book.
Unattended IPLs are the easiest type of IPL to perform because there is nothing to do other than turn on the CPU. Make sure the key lock on the CPU's control panel is in the NORMAL or SECURE position; the i5 takes care of the rest.
When you perform an unattended IPL, the i5 eventually shows the sign-on display at the system console and, if the start-up program specifies it, at all other display stations as well. Start-up programs are described later in this chapter.
You should perform unattended IPLs unless a compelling reason exists to perform an attended IPL. Keep your CPU's key lock in the NORMAL or SECURE position.