NMON is currently integrated to AIX, like topas, it's a real time performance monitoring tool.

NMON can also collect performance information, but depending on the duration, it reports into a static file.

You can for example monitor your machines on the last day, store the datas into a database and create graphics, using tools like :

nmon2rrd
nmon2graphite http://chmod666.org/index.php/nmon2graphite-graph-nmon-output-in-real-time/
nnmon
...
http://matthiaslee.com/node/38 (nmon analyser python)