index in use when any SQL access it...

Hi, ifx 11.50 FC9X6 , AIX 6.1 I'm looking about use of indexes on some tables. The mainly objective is check if this indexes still needed and who use it. Then I using the commands bellow (in my own scripts) to try reach my objective: onstat -g opn onstat -t onstat -g ppf The situation what I found: - With "onstat -g ppf" I identify one index have low use . so I'm trying indentify who use it and what SQL is. - With "onstat -t" I see few users accessing it. - With "onstat -g opn" (looking for the partnum of the idx) I get the sessions id and track the application. - I not found at the application code any SQL what justify the access over this indexes. Trying identify what SQL access this indexes I simulate the situation successfully at our test environment. Over this test environment, to try track what SQL is, I execute : - Activate SQL TRACE over my user - Activate explain dynamically (onmode -Y) at the session. - Then I run the application - At onstat -g opn and onstat -t , the index show the status of "in use" for my session - At the sql trace and explain, there is no reference for it. :( So, Why they is showed "in use" ????? My suspect is over the optimizer, when probably they check what index use and just keep it "opened" .... could be this ? Regards Cesar