The on success message is used in Form Actions - < On add / On Edit / On Delete > - On Success blocks to display a message on successful submission of Form data. By default, the message "Data Added Successfully" is displayed. If you want to customize this message, you have to specify the same in the success message string as shown below.
//specify the message here
success message "<specify message>";
The following script added to the Form Actions - On Add - On Success block of a Form, will display the message "Employee record added", when a record is added to the database.
success message "Employee record added";