onmode -F

Has anybody been facing a problem when running onstat -F We had problems with logical logs, they didn't got backed up. We are using onbar. After rebooting Informix everything has been always ok !. Now I tried onstat -F, because I think it's a kind of memory fragmentation problem. After pressing enter database got stucked. Nothing in Online.log. Dbaccess didn't work. Sessions from Baan didn't work. I had to give onmode -ky. It took 30 minutes to bring instance down. This is very big instance with 3-4 gig memory consumption (onstat -g seg). Lot of tables, not so much data. Application is baan in 3-tier setup. Version of IDS is 7.31.FC2 on HP/UX 11 N-class, 6 processors and 12g memory. I have onstat -p from that situation ( yes, onstat-commands were working !). Thank you !