IBM AIX Continuous Availability Features - IBM Redbooks

Component Trace uses mechanisms similar to system trace. Existing TRCHKxx and
TRCGEN macros can be replaced with Component Trace macros to trace into system trace
buffers or memory trace mode private buffers. These macros are CT_HOOKx and CT_GEN,
located in /usr/include/sys/ras_trace.h. Once recorded, Component Trace events can be
retrieved by using the ctctrl command. Extraction using the ctctrl command is relevant
only to in-memory tracing. Component Trace events can also be present in a system trace.
The trcrpt command is used in both cases to process the events.
2.3.10 Lightweight Memory Trace (LMT)
2.3.11 ProbeVue
2.3.12 Error logging
Lightweight Memory Trace is an efficient, default-on per CPU, in-memory kernel trace. It is
built upon the trace function that already exists in kernel subsystems, and is of most use for
those who have AIX source-code access or a deep understanding of AIX internals.
LMT provides system trace information for First Failure Data Capture (FFDC). It is a constant
kernel trace mechanism that records software events occurring during system operation. The
system activates LMT at initialization, then tracing runs continuously. Recorded events are
saved into per-processor memory trace buffers. There are two memory trace buffers for each
processor—one to record common events, and one to record rare events. The memory trace
buffers can be extracted from system dumps accessed on a live system by service personnel.
The trace records look like traditional AIX system trace records. The extracted memory trace
buffers can be viewed with the trcrpt command, with formatting as defined in the /etc/trcfmt
file.
For further details about LMT, refer to 3.2, “Lightweight memory trace” on page 57.
AIX V6.1 provides a new dynamic tracing facility that can help to debug complex system or
application code. This dynamic tracing facility is introduced via a new tracing command,
probevue, that allows a developer or system administrator to dynamically insert trace probe
points in existing code without having to recompile the code. ProbeVue is described in detail
in 3.8, “ProbeVue” on page 111. To show or change the ProbeVue configuration, use the
following command:
smitty probevue
Troubleshooting system problems is an important and challenging task for system
administrators. AIX provides an error logging facility for the runtime recording of hardware
and software failures in an error log. This error log can be used for informational purposes, or
for fault detection and corrective actions.
The purpose of error logging is to collect and record data related to a failure so that it can be
subsequently analyzed to determine the cause of the problem. The information recorded in
the error log enables the customer and the service provider to rapidly isolate problems,
retrieve failure data, and take corrective action.
Error logging is automatically started by the rc.boot script during system initialization. Error
logging is automatically stopped by the shutdown script during system shutdown.
The error logging process begins when the AIX operating system module detects an error.
The error-detecting segment of code then sends error information to either the errsave kernel
30 IBM AIX Continuous Availability Features