The Connect CDC (SQData) Keyed File Compare Capture aka "The Differ" determines the differences between two files of the same format and writes the Change data including both before and after images to a z/OS System LogStream. The zLog Publisher component then manages the captured data by communicating with downstream Engines via TCP/IP. Once an individual Unit-of-Work has been forwarded to all target Engines and consumed, the zLog Publisher marks as Done the data in the LogStream.
The Keyed File Compare Capture Agent can be run against both Keyed and non-keyed sequential files though the Engine will require a key to be identified for application to the target datastore. The CDC Datastore type used is VSAMCDC regardless of the actual source file system type.
This Capture agent is useful in extracting the specific changed records from large files that are updated on a regular basis (i.e. daily, monthly, etc.). Since the volume of changed data is typically very small compared to the total number of records in the file, downstream applications get access to the data faster and with fewer CPU cycles.
Finally, the Keyed File Compare can also be used to generate Initial load and refresh data for VSAM files normally captured by the VSAM Log Replicate Capture.
