Tracing Functions 
The trace tool helps you access information that is logged in while processing a function or an expression. Trace is a step-by-step explanation for processing a function. The information generated is also helpful for legal reasons. The trace details can be saved at runtime.
Example
You have a function and you can run the function for n times. If you want to see what has happened at a point of time, you can run the function for legal reasons and check if anything goes wrong. You can see the result at each step.
Prerequisites
Note
Use the trace tool for only those functions in which Internal Commit or External Commit options is selected under the Trace Mode field.
Procedure
Create a function or open an existing function.
More information: Creating a Function
Under the Properties tab, in the Trace Mode field, choose Internal Commit or External Commit option.
In the menu bar, choose
Tools 
Trace 
.In the Trace dialog box that appears, enter a username (optional) and choose the dates for the trace.
Choose Query to search for the function name.
In the Object Query dialog box that appears, you can either enter the name of the function in the Name field or enter the application name (in which the function is used) in the Application Name field.
Select the function for trace and choose Select .
The selected function name appears in the Function Name field.
Enter the time period for which you want to trace the function.
Choose Search.
The traced details appear under the Trace Details section.