You can configure multiple PowerExchange CDC Publisher "instances," each with its own set of checkpoint files, configuration files, log files, and Avro schemas. When you start a PwxCDCPublisher process, you specify the name of the instance to use. The instance name corresponds to a directory within the PowerExchange CDC Publisher installation. By default, the PowerExchange CDC Publisher installation creates the "instanceA" directory and its subdirectories. Consider adding instances to process change data in multiple streams for different sources or different targets or for load balancing.

The PowerExchange CDC Publisher reads extraction map information only at startup. If you edit the capture registrations and the associated extraction maps for the data sources, PowerExchange CDC Publisher does not automatically update the Avro schema. You must run the PwxCDCAdmin utility with the CLEAR parameter to remove the old Avro schema from cache. You can then run the utility again with RESET parameter to re-read the extraction maps and cache the updated Avro schema. After you restart the PwxCDCPublisher process, it can use the updated Avro schema in cache to generate messages in the latest schema format for transmittal to the target messaging system. For more information about PwxCDCAdmin utility parameters, see PwxCDCAdmin Utility - Command and Parameters.

If you start the PwxCDCPublisher process before the PowerExchage Logger for Linux, UNIX, and Windows has written at least one source change record to its log files, the Publisher Extractor process might end with an error. This issue is caused by a PowerExchange Logger reader limitation that pertains to the first run of the PowerExchange Logger.

PowerExchange sends change data from successful units of work (UOWs) to the CDC Publisher in commit order. The PowerExchange CDC Publisher maintains this order when streaming messages to the target messaging system.

The CDC Publisher processes a stream of change records in a manner that is independent from transaction start and end points. If the CDC Publisher terminates or connectivity to the target messaging system is lost before all of the changes in a transaction are processed, the target will have only some of the changes until you restart the CDC Publisher so that it can send the remaining changes in the transaction. The CDC Publisher process will restart from the last checkpoint position recorded in the checkpoint file by default.

The PowerExchange CDC Publisher can filter source tables or objects by using the filtering criteria you specify in the Extract.captureConsumerIncludeNameList and Extract.captureConsumerExcludeNameList properties in the cdcPublisherPowerExchange.cfg configuration file. However, the CDC Publisher cannot filter source columns.

The PowerExchange CDC Publisher does not automatically exclude extraction maps that are associated with capture registrations that have the status of Inactive, History or Suspended. If no change data is available, the CDC Publisher does not publish change data for the registered source objects. If you will never use these deactivated capture registrations or their associated extraction maps to capture and publish change data, you can exclude the extraction maps in the CDC Publisher to reduce resource consumption. Before you define the exclusion filter, ensure that any change data that was previously captured for the source object has been published to the target messaging system. After you define the exclusion filter, you must restart the CDC Publisher process for the filter to take effect. If you plan to reactivate a suspended registration, first remove the exclusion filter for the associated extraction maps. Then restart the CDC Publisher process and reactivate the registration.