System Startup, Configuration, and Shutdown Reference Manual (32650-90907)

Chapter 2

Initiating System Activity

Determining and Selecting Input and Output (I/O) Paths

The system identifies adapter interfaces to a system bus and the associated devices by an I/O path. The I/O

path is the address of the interface hardware and the physical path to reach a device.

When the system is reset or the power is turned on, hardware routines read and initialize the I/O paths

needed to boot the system. These boot paths consist of the primary boot path, for booting from disk-resident

software; the alternate boot path, for booting from a system load tape; and the console boot path, for locating

console operator intervention.

Boot paths for the primary boot device, the alternate boot device, and the console are shown as numbers

separated by periods or forward slashes.

There are several ways to determine the I/O path for devices that are attached to the system:

• Generate a list of paths for devices that have already been configured by using the LPATH command of the

SYSGEN utility IO Configurator. SYSGEN does not tell you if the configured device is active or available.

During the system boot (using the ISL START command), information on which paths have been

configured and which devices are available or not available is listed as the “System State at Boot Time.”

(For more information on the system state, refer to Chapter 3, “System Startup Functions,” and

Appendix B, “Startup, Dump, and Shutdown Listings.” For more information on SYSGEN, refer to

Chapter 4, “Using the System Generator (SYSGEN).”)

• Use the ISL utility, IOMAP, to list the devices on the system. (For more information on IOMAP, refer to

Appendix E, “Verifying Attached Devices.”) For 9X8LX and 9X8RX systems, use the ODE utility to list

devices on the system.

• For the N-class and A-class systems, the BCH (Basic Console Handler) SEA command in the Main Menu

lists the disk and tape devices physically present on the system.