The action that. the machine check handler takes for a given situation
is determined by the error itself,' the operating environ.ent of VM/370, and whether the system was performing a CP function or a virtual machine function --or the system was not performing at all (a loaded wait state
condition when the error occurred). Figure 24 clarifies the action the
system takes for the gi ven si tua tions. I VM/370 Processing IVirtual Machine processing I I I I I Error Condition I uniprocessor attached processor I uniprocessor attached processor I I I I I Main Attached Main I attached I I I I Invalid machine I 1 1 1 1 1 1 I check interrupt I code Invalid PSi 1 1 1 1 3 3
data
Register, 1 1 1 3 3 Program Ilask instruction
address invalid
System damages 1 1 1 1 3 3
TOD or CPU 1 1 1 1 1 3,4
Clock Errors
Multibit 1 1 1 3,2 3,2 3,2 (solid) Storage error
Multibit 1 1 1 3,2 3,2 3,2
(intermi ttent)
storage error Storage Protect 1 1 1 3 3 3 Key (solid)
failure Storage Protectl 2 2 2 2 2 2
(intermittent) I failure I I Malfunction I 5 1 1 5 1 3,4
alert I Channel 1 1 1 1 1 1
inoperative Legeng: I 1 = load wait state PSi I 2 = refresh for retry operation I 3 = terminate the virtual .achine I 4 = automatic processor recovery I 5 = Not applicable
Figure 24. Condition/Action Table for Uncorrectable Errors CP Introduction 1-177

For external interrupts that can occur in attached processor .ode
(time-of-day sync check, malfunction alert, external call, and emergency signal), DMKPSAEX gives control to DMKEXTSL. DMKEXTSL does the
following for each kind of interrupt: Malfunction alert • Call DMKMCTMA, which will either load a disabled wait state on the
appropriate processor or initiate automatic processor recovery, to
allow the system to run in uniprocessor mode. If a user was running
at the time of the malfunction alert he is terminated. SHUTDOWN Emergency Signal Issued to the attached processor prior to shutting the system down. • Turn off APUOPER in each PSA to indicate that the attached processor
is not operational. • Load a 008 disabled wait PSi. • Disable channel zero. • Pass control to the dispatcher at DMKDSPRU. QUIESCE Emergency signal • Give control to the dispatcher at DftKDSPRU, which will load a wait PSW that is enabled for external calls only. SYNC Emergency Signal Issued by DMKCLKMP when the clocks are no longer synchronized (low order
synchronization). • Give control to DMKCLKAP to synchronize the
processor. If the set clock fails, the
terminated with a CLK003 abend.
CLKCHK Emergency Signal clock on
attached
the attached
processor is • Give control toDMKCLKCC. If the clock on the attached processor is
not synchronized with the main processor (high order synchronization)
or is not set, then a flag is set to cause DMKCLKMP on the main processor to synchronize the clocks. The attached processor is then
put in a wait state enabled for external interrupts. If the clock is not working, the attached processor is terminated with a CLK003 abend. APR External Call • Give control to DMKMCTPR to allow the system to run in uniprocessor mode. RESUME External Call
Cancels a previous QUIESCE. • Give control to the dispatcher at DMKDSPRU. 1-178 IB" V"/370 System Logic and Problem Determination--Volume 1