It is not uncommon that an inefficient SQL statement causing overall performance problem. In that scenario, first you need to identify the problematic SQL, next find out the user and application that executing the SQL. Here is a glimpse to address the second part of the problem.
There are different possible ways to find out the user and application running a particular SQL. The ‘onstat -g ses <sessionid>’ command is the simple way figure out the application that running a SQL. Do you notice any thing new in the following ‘onstat -g ses <session id>’ output?