Hi sudheer kore
CDC is basically a technical term - Change data capture. We use a few approaches to work capture changed data during ETL process. This can be called incremental approach/ delta loading of data.
Source Based CDC
-Using a timestamp, date, datetime, or int column to uniquely identify the next "band" of rows to be loaded into the delta process in combination with a status table, global variable, and where clauses of the query transform. This is demonstrated in the Tutorial file provided with Data Services in the CDC chapter.
-Using the Database native CDC functionality, available in Oracle, SQL Server and I believe Attunity
Changes are replicated to change tables in the source, marked as insert/update/delete. Data Services can natively read these tables through the use of CDC Datastore objects and Map_CDC_Operation transform.
Target Based CDC
-Must be used if the methods above are not available. The Table_Comparison transform is capable of comparing all source records to the target table to determine if an INSERT or UPDATE is required for that row.
Few links that would explain this better
Source Versus Target Based Change Data Capture
Map_CDC_Operation in Data Services
http://sapsimplified.com/sap-bods/map-cdc-operation-transformation/
Regards
Anil Kumar Mehar G