IBM System/370 145 Manual page 217

eliminating the necessity for compl.ete system unavail.ability while many
types of I/O errors are being diagnosed.
MICRODIAGNOSTICS
The diagnostics provided are divided into several groups. They are
the resident diagnostics, the 'Balsic group, the Extended group, the
Manual sections. and the Integralted File Adapter section.
The resident diagnostics, whi.ch are loaded as part of the basic
system microcode, are the CPU Checkout and the Storage Scan/Storage
Clear routines. The CPU Checkoult routine is automatically executed
following power-on reset, IMPL, IPL, and system reset operations to test
certain CPU functions., ~he CPU Checkout routine stops upon detecting an
error, and other diagnostic rout,ines must then be executed to pinpoint
the suspected malfunctioning replaceable unit. The Storage Scan and
storage Clear routines are executed by setting the diagnostic switch on
t,he system control panel to the desired function.
The other mic,rodiagnostics provided are fault-locating tests that
attempt to identify the failing replaceable component. These
microdiagnostics are distributed on console file disk cartridges. They
are loaded from the console file and use the system console device for
communication.
The Basic group is designed bD be used before the Extended group.
The initial sections of the Basic group are executed directly from the
console file, rather than from control storage, and they require only a
minimal amount of hard core circuitry to be operational. Using this
basic circuitry, a ftbuilding blolck" technique of verifying the circuitry
is employed, and eventually, con°trol storage is loaded with the
remaining Basic group diagnostic:EI, which are then executed under normal
CPU control. The Basic group de'tects and locates failures in the basic
CPU and the system console devicle.
The Extended group tests otheJr CPU hardware (retry, timers. machine
check, etc.) and the channels. ~rhe tests are designed to be executed in
a building block sequence also,
2:;0
that untested hardware is never used
in testing out another hardware section. The Manual sections require
manual intervention and are desi~1ned to test system control panel
functions, storage, and the syst4~m console device.
50:20
RAS
SUMMARY
The degree to which an instalJLation benefits from available
RAS
features depends in part upon thE:!ir proper implementation. It is
desirable for Model 145 users to design a system that includes RAS
features and to become involved in the implementation and use of
maintenance procedures and aids. Specifically, the user can:
• Include OLTEP and OLT's in his operating system (optional for OS
users)
• Plan system and program recovery procedures (use of
checkpQint/restart and warm sltart facilities)
• Have operating personnel perform normal hardware maintenance
procedures, such as the pericdic cleaning of tape unit heads.
Proper system hygiene should be maintained, in general •
• Implement an effective progra,m of operator training so that the
number of system malfunctions. that occur because of operator error
is minimized
A Guide to the IBM System/370 Mod.el
145
207