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Trigger mode

This mode is available for the following databases: MySQL, Oracle, DB2, PostgreSQL, Sybase, MS SQL Server, Informix, Ingres, and Teradata.

The Trigger mode places a trigger that launches change data capture on every monitored source table. This, by turn, imposes little modifications on database structure.

With this mode, data extraction takes place at the same time the Insert, Update, or Delete operations occur in the source tables, and the change data is stored inside the database in change tables. The changed data, thus captured, is then made available to the target system(s) in a controlled manner, using subscriber views.

In Trigger mode, CDC can have only one publisher but many subscribers. CDC creates subscriber tables to control accessibility of the change table data by the target system(s). A target system is any application that wants to use the data captured from the source system.

The below figure shows the basic architecture of a CDC environment in Trigger mode in Talend Studio.

Basic architecture of a CDC environment in Trigger mode.

In this example, CDC monitors the changes made to a Product table. The changes are caught and published in a change table to which two subscribers have access: a CRM application and an Accounting application. These two systems fetch the changes and use them to update their data.

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