at first guess I'd say you have a memory leak on that computer
ie an application is accquiring memory and not releasing it whn its done.
you don't say if its the server or a workstation/local machine
if its a server then I'd guess you may have either hardware problems or somethign odd going on
however I'd guess its a local machine/workstation problem. and that probably means its a piece of software you are using or developing that is causing the issues. even commercial produced software can have memory leaks (IIRC Macromedia Fireworks had soem serious memory leak issues)
if you are developing software then it could wel be that you are not correctly releasing memory through setting objects to null, close connections and so on.
I'd be surprised if its actually a DB2 problem as I wouldnt' expect it to be instantiating a JRE frequently.
a temporary fix can be to shut the machine down and reboot, that will automatically start with a fresh memory map.
I'd rather be riding on the Tiger 800 or the Norton