The Delta Engine feature is available to Connectors in Iterator mode. If enabled from the Iterator's Delta tab, the Delta engine feature uses the System Store to take a snapshot of data being iterated. Each successfully read Entry is compared with the snapshot database called the Delta Store to see what has changed. Based on the differences between the read Entry and the Entry stored in the Delta store, a new Entry called a Delta Entry is created by the Delta Engine. This Entry is tagged with special delta operation codes to indicate what has changed, and how.
Delta mode is a Connector mode which enables a connector to “understand” and use the delta operation codes. A connector in this mode uses the delta operation codes of a received Delta Entry to determine what type of change needs to be applied to the connected system. The Delta mode supports all types of modifications - add, modify and delete. This mode is used to facilitate synchronization between different systems (for example, synchronizing two LDAP servers on different machines).
Attention: The Delta Engine introduces an underlying local repository for storing snapshots of data in order to compute changes during the synchronization process. The data source that is being scanned for changes becomes the master in a master-slave relationship, and it is then vital that all changes made to the slave (for example, the Delta store) be made using the Delta mechanism, and not by directly manipulating the underlying database table. Otherwise, the Delta snapshot information that Tivoli Directory Integrator maintains becomes inconsistent, and the Delta Engine fails.