In order to change your database manager from a passive system to an active one, use the capabilities embodied in a trigger function. A trigger defines a set of actions that are activated or triggered by, an update operation on a specified base table. These actions may cause other changes to the database, perform operations outside DB2 (for example, send an e-mail or write a record in a file), raise an exception to prevent the update operation from taking place, and so on. This chapter discusses the following topics which you need to understand to use triggers effectively in your applications: