IBM Power 780 Technical Overview And Introduction page 206

Online diagnostics, when installed, are a part of the AIX or IBM i operating system on the disk
or server. They can be booted in single-user mode (service mode), run in maintenance mode,
or run concurrently (concurrent mode) with other applications. They have access to the AIX
error log and the AIX configuration data. IBM i has a service tools problem log, IBM i history
log (QHST), and IBM i problem log.
The modes are as follows:
Service mode
This mode requires a service mode boot of the system and enables the checking of
system devices and features. Service mode provides the most complete self-check of the
system resources. All system resources, except the SCSI adapter and the disk drives
used for paging, can be tested.
Concurrent mode
This mode enables the normal system functions to continue while selected resources are
being checked. Because the system is running in normal operation, certain devices might
require additional actions by the user or diagnostic application before testing can be done.
Maintenance mode
This mode enables the checking of most system resources. Maintenance mode provides
the same test coverage as service mode. The difference between the two modes is the
way that they are invoked. Maintenance mode requires that all activity on the operating
system be stopped. The shutdown -m command is used to stop all activity on the operating
system and put the operating system into maintenance mode.
The System Management Services (SMS) error log is accessible on the SMS menus.
This error log contains errors that are found by partition firmware when the system or
partition is booting.
The service processor's error log can be accessed on the ASMI menus.
You can also access the system diagnostics from a Network Installation Management
(NIM) server.
Alternate method: When you order Power Systems, a DVD-ROM or DVD-RAM might be
optional. An alternate method for maintaining and servicing the system must be available if
you do not order the DVD-ROM or DVD-RAM.
The IBM i operating system and associated machine code provide Dedicated Service Tools
(DST) as part of the IBM i licensed machine code (Licensed Internal Code) and System
Service Tools (SST) as part of the IBM i operating system. DST can be run in dedicated mode
(no operating system loaded). DST tools and diagnostics are a superset of those available
under SST.
The IBM i End Subsystem (ENDSBS *ALL) command can shut down all IBM and customer
applications subsystems except the controlling subsystem QTCL. The Power Down System
(PWRDWNSYS) command can be set to power down the IBM i partition and restart the
partition in DST mode.
You can start SST during normal operations, which keeps all applications running, by using
the IBM i Start Service Tools (STRSST) command (when signed onto IBM i with the
appropriately secured user ID).
With DST and SST, you can look at various logs, run various diagnostics, or take several
kinds of system dumps or other options.
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IBM Power 770 and 780 (9117-MMD, 9179-MHD) Technical Overview and Introduction