Is it possible to modify data in database?

Generally, BIRT (and reporting in general) is used to display data to the user so BIRT does not include any help in writing the data back to a database... Having said that, BIRT does fire events, and allows you to access Java classes all throughout the report generation process so you could write your own code that modifies a database during generation

...or if you want the person viewing the report to send something back to a database, BIRT also allows you to include HTML into the report.... so you could, for example, let the user reorder parts right from the report when they notice the inventory is low. In this example, a simple HTML form is used to send data back to a Java Servlet, or really anything that accepts a form post, where you could write it to a database.