CDC Guide for Linux, UNIX, and Windows

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How the PowerExchange Logger Determines the Start Point for a Cold Start

When you cold start a PowerExchange Logger for Linux, UNIX, and Windows process, it uses the RESTART_TOKEN and SEQUENCE_TOKEN parameters, if present, in the pwxccl configuration file to determine the point in the change stream at which to start reading changes.

Based on how you set these parameters, the PowerExchange Logger starts from one of the following points in the change stream:

If you enter valid token values in the RESTART_TOKEN and SEQUENCE_TOKEN parameters, the PowerExchange Logger starts from the point in the change stream that the token values specify. Use this method to start the PowerExchange Logger from a specific point.

If you do not define the RESTART_TOKEN and SEQUENCE_TOKEN parameters, the PowerExchange Loggers starts from the current end-of-log (EOL), or current point in time in the change stream.

You can generate restart and sequence tokens for the current EOL by running the DTLUAPPL utility with the RSTTKN GENERATE parameter or by performing a database row test with the SELECT CURRENT_RESTART SQL statement in PowerExchange Navigator.

If you enter only zeroes (a single 0, or an even number of 0s) in the RESTART_TOKEN and SEQUENCE_TOKEN parameters, the PowerExchange Logger processing starts from one of the following start positions, depending on the data source type:

For DB2 for Linux, UNIX, and Windows sources, processing starts from the position at which the DTLUCUDB utility created the DB2 catalog snapshot to initialize the PowerExchange capture catalog table. However, you can change this default restart position with the DTLUCUDB UPDTDRP command.

For Microsoft SQL Server sources, processing starts from the position of the oldest available data in the distribution database.

For PowerExchange Express CDC for Oracle sources, processing starts from the beginning of the most recent Oracle archive log.

For PowerExchange Oracle CDC with LogMiner sources, processing starts from the position that corresponds to the most recent Oracle LogMiner dictionary dump.

For remote DB2 for i5/OS sources, processing starts from the beginning of the oldest receiver in the current chain of receivers.

For remote z/OS data sources, processing starts from the beginning of the PowerExchange Logger for MVS active log files.

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Table of Contents

CDC Guide for Linux, UNIX, and Windows

CDC Guide for Linux, UNIX, and Windows

How the PowerExchange Logger Determines the Start Point for a Cold Start

How the PowerExchange Logger Determines the Start Point for a Cold Start