VSAM supports both Undo and forward recovery logging using two different LogStreams. Connect CDC (SQData) capture uses the CICS VSAM LOGREPLICATE function which logs changes in the form of both before-image and after-images as they are committed by CICS on-line applications.
While the same LogStream can be used for both the online CICS VSAM LOGREPLICATE Function and the batch CISC/VR Replication Logging Function, some installations chose to use two different LogStreams. The CDCzLog Publisher component can manage one or more LogStreams containing change data from both online and batch environments. The default behavior of the publisher is to leave the captured data in the LogStream(s) until Engines often running on other platforms, acknowledge that the published data has been applied to target datastores. At that time the publisher will clean as in remove the data captured from the LogStream.
There are a number of other factors involved when the VSAM LOGREPLICATE Function is used for third party Data Capture products including:
- Recovery Logging (forward and undo)
- VSAM RLS (Record Level Sharing)
- Batch VSAM Capture
The configuration instructions included here describe the minimum configuration requirements. Precisely recommends consultation with systems personnel responsible for CICS and VSAM operations to ensure the configuration required for Capture considers their other requirements. For example, if Forward Recovery capabilities are required for either CICS VSAM or batch VSAM processing then the Publisher must be instructed not to clean the LogStreams containing the data used for Replication. Please contact Support before implementation to discuss various configuration options including the utilization of multiple CDCZlog Publisher agents.
Notes:
- Cleaning can be turned off/disabled by specifying the keyword --ptk=8 in the Publisher startup command parameter.
- As previously stated, the Coupling Facility (CF) should be used if CICS is running in a Sysplex Environment. A DASD based LogStream configuration should ONLY be used if CICS is running on a single LPAR and if it is being accessed by Capture agents on a different LPAR.