When a PowerCenter CDC session runs, it extracts change data from the log files instead of from the change stream.

The PowerExchange Logger can capture change data from Db2 database logs, a Microsoft SQL Server distribution database, MySQL binary logs, Oracle redo logs, or PostgreSQL replication store table that records changes retrieved from a logical replication slot. If you use the remote logging feature, a PowerExchange Logger process on Linux, UNIX, or Windows can also process data from data sources on IBM i or z/OS systems.

Use the PowerExchange Logger to reduce the overhead of CDC processing. With the PowerExchange Logger, PowerExchange accesses the source database fewer times to read change data, which reduces database I/O. Also, because change data is extracted from the PowerExchange Logger log files, you do not need to extend the retention period for source database log files to accommodate CDC processing.

You must run one PowerExchange Logger process for each source type and instance, as defined in a registration group. The PowerExchange Logger can run on the source database server, PowerCenter Integration Service machine, or another system in either continuous mode or batch mode.

Multiple PowerExchange Logger instances can run under the same PowerExchange Listener and dbmover.cfg configuration. However, because a single dbmover.cfg can contain a maximum of eight CAPI_CONNECTION statements, the number of source instances and PowerExchange Logger instances that can run under a single Listener and dbmover.cfg is limited. For more information, see CAPI_CONNECTION Statements.

When you create capture registrations for data sources, including IBM i and z/OS data sources for which processing is offloaded, set the

Condense

option to

Part

. The PowerExchange Logger supports only partial condense processing. For IBM i or z/OS data sources, if you set the

Condense

option to

Full

in capture registrations, the PowerExchange Logger ignores the registrations and does not process change data from those sources.

For each PowerExchange Logger process, you must define a configuration file. PowerExchange provides a sample configuration file named pwxccl.cfg. The configuration file contains parameters for controlling the PowerExchange Logger and for identifying the source instance. Use the COLL_END_LOG parameter to control whether the PowerExchange Logger runs in continuous mode or batch mode.

When PowerCenter CDC sessions run, the PowerExchange Log Reader process extracts change data from the PowerExchange Logger log files in continuous extraction mode or batch extraction mode.

You can secure sensitive data that is stored in PowerExchange Logger log files, such as Social Security numbers, by enabling AES encryption of the log files. In the PowerExchange Logger configuration file, you can select the AES encryption algorithm that you want to use. To enable encryption, you must also specify an encryption password either in the PowerExchange Logger configuration file or in the pwxccl command that you use to cold start the PowerExchange Logger from the command line. If you specify the encryption password in the pwxccl command for a cold start and need to restore the CDCT file later, you must enter the same encryption password for the restore operation.