Different Query plan when run on different server

I was investigating a slow running query and couldn't understand the path it was taking so I ran it on a testing server as update stats hadn't been run on one of the main tables in the query. This server has a restored copy of the live DB albeit one week old. The live server is a Sun 6800, Solaris 9, 16 CPUs and the Test server is a V440, Solaris 10 with 4 CPU. I'll post sqexplain output if someone really wants it but can anyone suggest an explanation as to why I am seeing this behaviour. BTW Running dostats on the table (124M rows) took almost 6 hours on live yet on the test server it took 3hrs 25mins. The only differences with Informix on the two servers is one is active 24*7 and the onconfig parameters to reduce the size of SHM and locks etc. Regards Colin There are 10 types of people in the world, those that understand binary and those that don't