Identifying problem sql's via onstat

Has anyone written a unix or awk script to identify the link between a running unix processes and sql statements which are effecting performance. I can manually run onstat -u to give me the session id andthen onstat -g ses sessid to give me that specific sql. But I can't identify the sessions that are causing the greatest drag on performance as they occur. Read/write statistics from onstat -u don't show me indexing/lock contention problems. Thanks Steve Gould