IBM AIX Continuous Availability Features - IBM Redbooks

service and errlast kernel service for a pending system crash, or to the errlog subroutine to
log an application error, where the information is, in turn, written to the /dev/error special file.
The errlast kernel service preserves the last error record in the NVRAM. Therefore, in the
event of a system crash, the last logged error is not lost. This process then adds a time stamp
to the collected data.
The errdemon daemon constantly checks the /dev/error file for new entries, and when new
data is written, the daemon conducts a series of operations. Before an entry is written to the
error log, the errdemon daemon compares the label sent by the kernel or application code to
the contents of the error record template repository. If the label matches an item in the
repository, the daemon collects additional data from other parts of the system.
To create an entry in the error log, the errdemon daemon retrieves the appropriate template
from the repository, the resource name of the unit that detected the error, and detailed data.
Also, if the error signifies a hardware-related problem and the Vital Product Data (VPD)
hardware exists, the daemon retrieves the VPD from the Object Data Manager (ODM).
When you access the error log, either through SMIT or by using the errpt command, the
error log is formatted according to the error template in the error template repository and
presented in either a summary or detailed report.
Most entries in the error log are attributable to hardware and software problems, but
informational messages can also be logged. The errlogger command allows the system
administrator to record messages of up to 1024 bytes in the error log.
Whenever you perform a maintenance activity, such as clearing entries from the error log,
replacing hardware, or applying a software fix, it is good practice to record this activity in the
system error log; here is an example:
2.3.13 The alog facility
errlogger system hard disk '(hdisk0)' replaced.
This message will be listed as part of the error log.
The alog is a facility (or command) used to create and maintain fixed-size log files. The alog
command can maintain and manage logs. It reads standard input, writes to standard output,
and copies the output into a fixed-size file simultaneously. This file is treated as a circular log.
If the file is full, new entries are written over the oldest existing entries.
The alog command works with log files that are specified on the command line, or with logs
that are defined in the alog configuration database. Logs that are defined in the alog
configuration database are identified by LogType. The File, Size, and Verbosity attributes for
each defined LogType are stored in the alog configuration database with the LogType. The
alog facility is used to log boot time messages, install logs, and so on.
You can use the alog -L command to display all log files that are defined for your system.
The resulting list contains all logs that are viewable with the alog command. Information
saved in BOS installation log files might help you determine the cause of installation
problems. To view BOS installation log files, enter:
alog -o -f bosinstlog
All boot messages are collected in a boot log file, because at boot time there is no console
available. Boot information is usually collected in /var/adm/ras/bootlog. It is good practice to
check the bootlog file when you are investigating boot problems. The file will contain output
generated by the cfgmgr command and rc.boot.
Chapter 2. AIX continuous availability features 31