Online diagnostics can be run in three modes:
| Concurrent Mode | Allows the normal system functions to continue while selected resources are being checked. |
| Service Mode | Allows checking of most system resources. |
| Maintenance Mode | Allows checking of most system resources. |
Note: Online diagnostics are only supported on machines with AIX.
Concurrent mode provides a way to run online diagnostics on some of the system resources while the system is running normal system activity. Because the system is running in normal operation, some of the resources cannot be tested, such as:
Service mode provides the most complete checkout of the system resources. This mode also requires that no other programs be running on the system. All system resources, except the SCSI adapter and the disk drives used for paging, can be tested. However, note that the memory and processor are only tested during Power On Self Tests (POSTs).
Service Mode is entered by booting AIX in service mode.
Maintenance mode provides the exact same test coverage as Service Mode. The difference between the two modes is the way they are invoked. Maintenance mode requires that all activity on the AIX operating system be stopped.
The shutdown -m command is used to stop all activity on the AIX operating system and put the AIX operating system into maintenance mode. After setting the terminal type, use the diag command to start Diagnostics.