onmode -z problems

Friends, Informixonians, countrymen... Help !! ODS 7.24.UC5 on HP-UX 11 running BaaN 6.1 We recently had to bounce our OnLine instance because a user was using in excess of 35k locks ( not usually a problem ) but had left the session in limbo. We attempted to kill the session using 'onmode -z' but it did absolutely nothing. There was still an active UNIX pid associated with the session so we thought this would have gracefully killed off the user and free all of the locks from the tables, reporting back to the UNIX session that the background porocess had been killed. We monitored the number of locks to see if they were being freed and 'onstat -p' reported that there were no roll-backs in operation. Having floundered around for about 10 minutes using 'onmode -Z' to kill an absolute address of a process, we eventually had to kill off the UNIX process - with no luck. We ( and Informix Tech Support ) concluded that the fastest way to clear the problem would be to bounce the engine but seemed a drastic measure when all we wanted to do was kill the session. Has anyone out there had the same problems and how did you get around it ?? All answers welcome TIA Sean