It makes use of the Informix utility 'onstat -u' to monitor the active usersessions in the database and displays a list of active sessions that were not existing the previous time the script was run or whose nreads or nwrites have changed since then. It stores a helpfile in the users $HOME for comparisson of the active sessions with the one's in the next run and it's designed for use with IDS 7.x / 9.x under Linux. A few alterations might be needed for use with other UNIX flavours.
With the 'sessid' number in the third column of the output you can further investigate a particular session with e.g. 'onstat -g ses sessid' or 'onstat -g sql sessid'.