IBM HANDBOOK 260 - Manual (Page 179)

Diagnostics and System Management Services 161
Error Log Analysis can be performed in Concurrent mode by selecting the
Problem Determination option on the Diagnostic Routine Selection menu.
To run On-line Diagnostics in Concurrent mode, just enter the following
command as root:
diag
After a period of time (up to three minutes), you will be presented with the
diagnostics initial screen.
6.3.3 Single-User Mode
Diagnostics can run from single-user mode (maintenance mode - although
this is different from booting into maintenance mode from a CD-ROM or a
tape). You can shut down your system into a single-user mode, which will
allow testing of many of your system resources that would normally be in use
while AIX is running. All the system resources, except the SCSI adapters and
disks used for paging, memory and processors, can be tested. Error log
analysis is available in this mode. Other users will not be allowed to log into
the system while the system is in single-user mode.
Logged on as root, you can enter diagnostics in single-user (maintenance)
mode by performing the following:
1. Stop all applications and log all users off the system.
2. Enter cd / to change into the root directory.
3. Enter the shutdown -m command.
4. When you see a screen similar to this one:
the system prompts you for the root password (if set).
5. Enter the root password.
6. At the command prompt (#), enter the diag command.
7. When the Diagnostic Operating Instructions area is displayed, follow the
instructions to check the desired resources.
After you have completed testing the system, press F3 to return to the
diagnostic operating instructions. Press F3 again to return to the AIX
operating system prompt. Press the Ctrl-D key sequence to log off from root.
Init: Single User Mode
Password: