CPU Usage tracking on Informix 7.x

On occassion we can see that the 'oninit' process associated with the CPU virtual processor of Informix is taking 100% of the CPU. Is there a good way now to track this down to which Informix sessions are actually using this CPU time? I wrote scripts that kind of give me an indirect idea. I take a snapshot of the syssesprof table of the sysmaster database, then run another snapshot a little later and compare the difference in number of lock requests. Is there a better, more direct way to track down CPU usage to individual sessions?