Update: July 2005
Date: July 7, 2002
Here are three AIX performance tools from IBM. The tools are free, and provided "As-Is" without support. The "nmon" tool was listed in a previous tip. The Capactiy Planning and AIX 5 Performance are new.
No longer available. http://www-1.ibm.com/servers/esdd/articles/free_tools/index.html
Updates: ISV Capacity Planning Tools for pSeries
pSeries Sizing and Capacity Planning; A Practical Guide
nmon Analyzer: http://www-106.ibm.com/developerworks/eserver/articles/nmon_analyser/ (Windows Excel macro to create spreadsheet)