NonStop Operating System Event Management Programming Manual

Low-Level I/O Event Messages (ZGIO)
HP NonStop Operating System Event Management Programming Manual—520372-020
3-4
Channel-Related Events
Channel-Related Events
Channel-related events describe the operation and performance of the processor I/O
channels connected to a specific processor. These events report errors detected by the
channel hardware and communications errors between the channel and device
controllers. Channel-related events do not identify a specific device; you can assume
that they affect all controllers connected to the reporting processor’s I/O channel.
The operating system monitor process reports channel-related events.
Topics:

Special Channel Interrupt Events on page 3-4

I/O Trace Table on page 3-4
Special Channel Interrupt Events
Errors detected by a processor’s channel microcode that cannot be isolated to a
particular device are reported to the processor’s instruction processing unit (IPU)
through the special channel error interrupt, which is system interrupt vector (SIV) #0.
These events are interpreted by the special channel error (SCHANL) interrupt handler
and then transmitted to the monitor process.
I/O Trace Table
To avoid excessive processing by the interrupt handler, some low-level I/O events are
detected in the interrupt environment but are reported by the monitor process. The
monitor process uses the I/O trace table to capture a consistent view of activity on the
I/O channel when an error occurs.
The I/O trace table is kept current by the instruction microcode for the EIO, IIO, and
HIIO instructions. In addition to these instructions, operating system software can also
add software trace entries for I/O-related events. When an interrupt handler detects an
exceptional condition, the operating system freezes the current state of the I/O trace
table.
Device-Related or Controller-Related Events
Device-related or controller-related events report:

Failures of devices and controller hardware

Communications errors between a device controller and an I/O device

Communications errors between a controller and an I/O channels
You can assume that events that refer to the operation of a device controller affect all
devices connected to that controller.