CDC Guide for z/OS

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IMS Log-Based Change Data Capture

The IMS log-based ECCR asynchronously captures change data from closed IMS archive logs (SLDSs) for a registered IMS database.

The ECCR passes the changes to the PowerExchange Logger for z/OS. After the PowerExchange Logger logs the changes to its log files, the changes are available for extraction processing. Based on specific parameters, the ECCR periodically inspects the IMS RECON data sets for new archive logs to process.

The IMS log-based ECCR runs in a separate address space either continuously or in batch mode. Because the ECCR runs within a multitasking environment, data capture, processing, and delivery can proceed in parallel.

During initialization, the ECCR reads capture registration information from the CCT data set to determine the segments in an IMS database that are registered for change capture. For each source database, you must complete the following tasks in the IMS environment:

Change the DBD to include the EXIT statement.

Because the IMS log-based ECCR reads closed IMS archive logs, a delay occurs between the time a change is made and the time the change is captured. The length of this delay depends on the following factors:

How quickly IMS archives the active logs after a change is made.

How frequently the IMS log-based ECCR checks for new archive logs.

PowerExchange transforms the captured changes into a PowerExchange internal format, which is essentially the same for all data sources.

If the IMS log-based change capture stops for any reason and updates to the IMS database continue, PowerExchange can resume change data capture from where it left off after you correct the problem and start change capture again. No changes are lost.

The IMS log-based ECCR can capture change data from complex tables. A complex table includes records for multiple segments in the IMS database hierarchy. If you need to capture change data from a complex table, do not use IMS field (FLD) calls to make changes to a low-level segment in the complex table. In this case, IBM IMS cannot provide the data for the parent segments. Conversely, if you need to allow FLD calls against the source database, Informatica recommends that you do not define complex tables as sources. If you must use complex tables with FLD calls, contact Informatica Global Customer Support to determine the best strategy for getting change data from the parent segments.

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CDC Guide for z/OS

CDC Guide for z/OS

IMS Log-Based Change Data Capture

IMS Log-Based Change Data Capture