ST05 is very effective tool for abap developers. When can be used?
– if You want to find tables . For example, You know that some data are shown in standard transaction. Run ST05 , activate the trace and then run the standard transaction in other window. When done, go back to ST05 and show trace. In 95% of issues , You will see all relevant tables.
– If You want to check the performance. If the report created by You got performance issue, or the same cn be with the standard SAP program, run ST05 , activate the trace and run your report or another transaction. When done, run ST05 again and show the trace. You will see the performance of tables.