IBM AIX Continuous Availability Features - IBM Redbooks

2.3.6 Parallel dump
2.3.7 Minidump
An AIX system generates a system dump when a severe unrecoverable error occurs. System
dumps can also be user-initiated by users with root user authority. A system dump creates a
picture of your system's memory contents. However, systems have an increasingly large
amount of memory and CPUs, and larger systems experience longer dump times. For this
reason a new feature, parallel dump, was introduced in AIX V5.3 TL5.
A new optimized compressed dump format has been introduced in AIX V5.3. The dump file
extension for this new format is .BZ. In this new compressed dump file, the blocks are
compressed and unordered; this unordered feature allows multiple processors to dump
parallel sub-areas of the system. Parallel dumps are produced automatically when supported
by the AIX release.
Important: The new file format for parallel dump is not readable with uncompress and zcat
commands.
The new dmpuncompress command must be used instead.
In order to increase dump reliability, a new -S checking option, to be used with the -L option
for the statistical information on the most recent dump, is also added to the sysdumpdev
command. The -S option scans a specific dump device and sees whether it contains a valid
compressed dump.
sysdumpdev -L -S
The dump must be from an AIX release with parallel dump support. This flag can be used
only with the -L flag. Additional options can be found and modified in SMIT via smitty dump.
The minidump, introduced in AIX V5.3 TL3, is a small compressed dump that is stored to
NVRAM when the system crashes or a dump is initiated, and is then written to the error log on
reboot. It can be used to see some of the system state and do some debugging if a full dump
is not available. It can also be used to obtain a quick snapshot of a crash without having to
transfer the entire dump from the crashed system.
Minidumps will show up as error log entries with a label of MINIDUMP_LOG and a description of
COMPRESSED MINIMAL DUMP. To filter the minidump entries in the error log, you can use the
errpt command with the –J flag (errpt [–a] –J MINIDUMP_LOG). Minidumps in the error log
can be extracted, decompressed, and formatted using the mdmprpt command, as shown:
mdmprpt [-l seq_no] [-i filename] [-r]
More detailed information about minidump is available at the following site:
http://igets3.fishkill.ibm.com/DCF/isg/isgintra.nsf/all/T1000676?OpenDocument&Highlight=0,m
inidump
2.3.8 Trace (system trace)
The AIX trace facility is a powerful system observation tool. The trace facility captures a
sequential flow of time-stamped system events, thus providing a fine level of detail of system
activity. Events are shown in time sequence and in the context of other events.
Chapter 2. AIX continuous availability features 27