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nmon analyser — A free tool to produce AIX performance reports

Usage notes: The nmon_analyser tool is NOT OFFICIALLY SUPPORTED. No warrantee is given or implied, and you cannot obtain help with it from IBM.

The nmon_analyser tool is designed to work with the latest version of nmon, but it is also tested with older versions for backwards compatibility. The tool is updated whenever nmon is updated, and at irregular intervals for new function.

Benefits of the tool

The nmon_analyser tool is helpful in analyzing performance data captured using thenmon performance tool. It allows a performance specialist to:

  • View the data in spreadsheet form
  • Eliminate “bad” data
  • Produce graphs for presentation to clients

The tool also automatically produces graphs for each major section of output.

In addition, the tool performs analyses of the nmon data to produce:

  • Calculation of weighted averages for hot-spot analysis
  • Distribution of CPU utilization by processor over the collection interval — useful in identifying single-threaded processes
  • Additional sections for IBM TotalStorage® Enterprise Storage Server (ESS) vpaths showing device busy, read transfer size, and write transfer size by time of day
  • Total system data rate by time of day, adjusted to exclude double-counting of EMC hdiskpower devices — useful in identifying I/O subsystem and SAN (Storage Area Network) bottlenecks
  • Separate sheets for EMC Corporation (EMC) hdiskpower and ESS DS8000 (formerly FAStT) dac devices
  • Analysis of memory utilization to show the split between computational and non-computational pages
  • Total data rates for each network adapter by time of day
  • Summary data for the TOP section showing average CPU and memory utilization for each command

Installing the tool

  • The tool is distributed as a .zip file and contains .xlsm files, comprehensive user documentation, a sample input file, a shell script for aiding National Language conversions, and a Perl program for splitting large input files. Installation simply requires unzipping the package to an appropriate directory.

Obtaining the tool

The following download option is available:

Sample output

Main chart showing CPU and I/O utilization during the collection interval

Main chart showing CPU and I/O utilization during the collection interval:

Optional chart showing vpath service times

Optional chart showing vpath service times:


Comprehensive documentation is included in the distribution. Available in Microsoft Word, the documentation includes details of how to collect data from nmon, how to use the analyzer, national language issues, guidance on interpreting the data, and detailed explanations for all fields generated by nmon.


This article was originally written by Stephen Atkins and published on November 15, 2003.