CDC it typically done following a full load process that loads the destination tables with a copy of the data in the source tables at a certain point in time. CDC processing is then responsible for continually updating the target tables as changes happen to the source. Any CDC solution needs to ensure that full load and CDC processing is synchronized in order to ensure data consistency and avoid errors when applying records to the destination.

The Attunity Oracle-CDC for SSIS provides built-in synchronization that will automatically ensure consistency, where the full load package will set the starting position for the CDC package. In addition, it also supports advanced merge options when applying the changes to the destination (see documentation for more details). You can choose to use these options by checking it in the ‘Full Load’ screen in the Package Builder Wizard.

If you do not use this option then no synchronization takes place by itself and the Full Load package does change the last position that the CDC package uses as a marker in the stream of changes. In this case you need to put a process in place to ensure the CDC processing starts at the right place (for example: by resetting it to the timestamp in which the full load ran so it picks any change that was done at a later time).