The database system has an internal event dispatcher that is used for automatic functions in the database system, such as automatic extension of the data area and automatic updating of SQL optimizer statistics. The event dispatcher is switched on if one of these automatic functions is active. It requires its own event task.
Furthermore, users can use the event dispatcher function in Database Manager CLI, for example to define whether the system is to perform a certain action as soon as a particular event occurs in the database. In this way, you can define, for example, that on reaching a certain fill level of the database, the system sends a warning mail to the database system administrator and/or executes a complete data backup. You have to switch on this event dispatcher explicitly using a DBM command. It runs until you switch it off explicitly. If the database is transferred to the OFFLINE operating state, the system stops this event dispatcher. If the database is transferred subsequently to the ONLINE operating state, the system starts the event dispatcher again. This event dispatcher also requires its own event task.
The system requires event tasks if you execute event commands in Database Manager CLI. The value of available event tasks is distributed between automatic database functions and events. The system default value for the available event tasks is generally large enough to use automatic database functions and a number of events. If you want to use a larger number of events in your database, enlarge the values of the FloatingServiceTasks and PreservedEventTasks database parameters accordingly.
More information: Support Database Parameters