Performing a system trace in SAP means to run a program and log all the dynpros/screens we are visiting and the fields we are clicking or typing. This task is done automatically when creating a recording in transaction LSMW.
You can find this functionality in ST01.
External References
System Trace at SAP Help http://help.sap.com/saphelp_nw70/helpdata/en/1f/83114c4bc511d189750000e8322d00/content.htm