You can use PowerExchange in conjunction with PowerCenter to replicate change data from multiple sources of the same RDBMS type to multiple targets of different types in a single session.

The targets can be tables or files on the same system as the source or on other systems. The PowerCenter Integration Service can write data to tables in some RDBMSs as well as to flat files and XML files. If you installed PowerExchange or PowerExchange (PowerCenter Connect) products that provide connectivity to additional nonrelational or relational targets, you can also load data to those targets, for example, Db2 for z/OS tables, VSAM data sets, IMS segments, or WebSphere MQ.

You can run multiple instances of PowerExchange CDC components on a single system. For example, you might want to run a separate PowerExchange Logger for each source RDBMS to create separate sets of log files for each RDBMS type.

The following image shows a simple CDC configuration that uses real-time extraction mode to access change data directly from the change stream without the PowerExchange Logger:

In this real-time configuration, PowerExchange CDC uses the CAPXRT access method to capture change data from a SQL Server distribution database, Db2 database logs, and Oracle redo logs. When an extraction request runs, PowerCenter connects to the PowerExchange Call Level Interface (SCLI) to contact the PowerExchange Listener. The change data is passed to the SCLI and then to the PWXPC CDC Real Time reader. In this manner, the PowerCenter extraction session pulls the change data that PowerExchange captured. After the PWXPC reader reads the change data, PowerCenter uses the mapping and workflow that you created to transform the data and load it to the target. With this configuration, you can replicate change data from multiple sources in the same database or instance to multiple target tables in a single extraction process.

The following image shows a CDC configuration that uses the PowerExchange Logger in both batch extraction mode and continuous extraction mode:

In this configuration, the PowerExchange Logger captures change data from the change stream for Microsoft SQL Server, Oracle, and Db2 tables and writes that data to its log files. After the data is in the PowerExchange log files, the source RDBMS log files can be deleted, if necessary. When an extraction session runs, PWXPC contacts the PowerExchange Listener. The PowerExchange Listener reads the PowerExchange Logger log files and calls the SCLI on the PowerCenter Integration Service machine to transmit the change data to PowerCenter.

For some source tables, PWXPC extracts change data from the PowerExchange Logger log files in batch extraction mode with the CAPX access method. In this mode, the extraction session stops after it completes processing the log files. For other source tables, PWXPC extracts change data in continuous mode with the CAPXRT access method. In this mode, the extraction session extracts change data on an ongoing basis. In PowerCenter, you can create one source definition and one mapping that covers both extraction modes. However, batch and continuous extractions must run as separate sessions. For a batch extraction session, use a PWX CDC Change application connection. For a continuous extraction session, use a PWX CDC Real Time application connection. For example, you can run batch extractions to replicate change data to targets that need to be synchronized periodically, and run continuous extractions to replicate change data to targets that need to be synchronized in near real time. Batch and continuous extraction sessions can run concurrently.