There's a logging feature (Composite Audit Level, under 'Settings') in Oracle's Enterprise Manager Console. However, usually you will not enable it in production environment because the feature captures too much detail(even the payload!) for every transaction and hence could lead to low storage level issue if your "composite" is expected to process too many transactions every minute.
Nevertheless, we still need to capture at least one of two detail for each transaction and such detail can be very useful when coming to problem troubleshooting.
So what do we do without enabling the 'logging' feature? We use the "Composite Sensors". At code level, this composite sensor is a xml with the name "sensor.xml". At Enterprise Manager's level, an composite sensor icon will appear in each transaction line. Just click on that and it will open up a new window that shows the detail.