When you use PWX CDC application connections to extract change data, PowerExchange uses group source processing and reads the change stream in a single pass for all source definitions in the mapping.
When you run a CDC session, PWXPC passes a source interest list that contains all of the sources. PowerExchange uses the source interest list to determine the sources for which to read data from the change stream. When PowerExchange encounters changes for a source in the interest list, it passes the change data to PWXPC. PWXPC then provides the change data to the appropriate source in the mapping.
To create source definitions in Designer that can be used to extract change data, import source metadata by using one of the following methods:
Import a PowerExchange extraction map by using the Import from
PowerExchange
dialog box.
Import the table definitions from relational databases, by using either the
Import from PowerExchange
dialog box or the
Import from Database
dialog box.
Restriction:
To read change data for nonrelational sources, you must import extraction maps from PowerExchange.
Informatica recommends that you use extraction maps to create source definitions for all CDC sources. When you create source definitions from extraction maps, the mapping and session creation process is simpler for the following reasons:
The source definition contains the extraction map name, which eliminates the need to provide it when you configure the session.
The source definition contains the PowerExchange-defined CDC columns, which eliminates the need to add these columns to the source definition. The PowerExchange-defined columns include the change indicator and before image columns as well as the DTL__CAPX columns.
When you extract change data, PowerExchange uses group source processing for all source definitions in the mapping. All source definitions must be for the same data source type, such as DB2, IMS, VSAM, or Oracle. Do not include multiple data source types in the mapping. Otherwise, the session fails with message PWXPC_10080.
For example, you cannot run a CDC session that contains a mapping with both VSAM and IMS source definitions, even though the change stream is the same. To extract change data for both IMS and VSAM data sources, create a mapping and session for the VSAM sources and a separate mapping and session for the IMS sources. PowerExchange reads the change stream twice, once for the session with VSAM sources and once for the session with IMS sources.
If you create a workflow that contains multiple CDC sessions, PowerExchange uses a connection for each session, even if the sessions extract change data from the same change stream, such as the PowerExchange Logger for z/OS.