You can detect an event in a relational or non-relational table and propagate it to other processes using a Table Listener.

An elaborate polling technology enables the specification of SQL SELECT statements to execute on a periodic basis. After data is polled, it passes through the adapter for further processing.

Note: Event processing may be limited for some non-relational databases due to the functionality of the database and its interaction with the iWay server component. For more information on the iWay server component, see the iWay Data Adapter Administrator User's Guide or consult your DBA.

You can poll a relational or non-relational database directly and send the results to the appropriate port. You also can use the following advanced techniques to listen to a database event.

• Standard event processing with row tracking

  The listener polls a table, sends each newly inserted row to a destination you specify (known as the disposition), and uses a control table to track the row that was most recently read. The control table prevents the most recently read row from being read again during the next listening cycle.

  You can apply this flexible yet simple technique in most situations.

  For more information, see Standard Event Processing With Row Tracking.

• Standard event processing with row removal

  The listener polls a table, sends each newly inserted row to a destination you specify, and then deletes the new row from the table to prevent it from being read again during the next listening cycle.

  You apply this technique when the source table is used to pass data to the adapter, and the table rows are not required to persist. Rows are deleted as they are processed.

  For more information, see Standard Event Processing With Row Removal.

• Trigger-based event processing

  At design time, you assign triggers to a joined group of tables. At run time, the triggers write information about table changes to a common control table. The listener polls the control table and sends information about the table changes to a destination you specify. The listener deletes new rows from the control table to prevent them from being read again during the next listening cycle.

  You apply this technique when listening for events in a group of large joined tables, or when you must know whether a row was updated or deleted.

  For more information, see Trigger-based Event Processing.