The Delta mode is designed to simplify the application of delta information; that is, make the actual changes in a number of ways.
Firstly, Delta mode handles all types of deltas: adds, modifies and deletes. This reduces the number of data synchronization ALs to two Connectors: One Delta Detection Connector in the Feeds section to pick up the changes, and a second one in Delta mode to apply these changes to a target system.
Furthermore, Delta mode will apply the delta information at the lowest level supported by the target system itself. This is done by first checking the Connector Interface to see what level of incremental modification is supported by the data source1. If you are working with an LDAP directory, then Delta mode will perform Attribute value adds and deletes. In the context of a traditional RDBMS (JDBC), then doing a delete and then an add of a column value does not make sense, so this is handled as a value replacement for that Attribute.
This is dealt with automatically by the Delta mode for those data sources that support this functionality2. If the data source offers optimized calls to handle incremental modifications, and these are supported by the Connector Interface, then Delta mode will use these. On the other hand, if the connected system does not offer "intelligent" delta update mechanisms, Delta mode will simulate these as much as possible, performing pre-update lookups (like Update mode), change computations and subsequent application of the detected changes.
Parent topic: Delta mode
1 Note that the only Connectors that support incremental modifications are the LDAP and JDBC Connectors, since LDAP directories provide this functionality.
2 Also, you
can control these built-in behaviors through configuration parameters
and Hook code.