CDC Guide for z/OS

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Creating Restart Tokens for Extractions

Before you begin extracting change data, you must create restart tokens to indicate the extraction start point.

When generating restart tokens, consider the following points:

The optimal start point matches the point in the change stream at which you last synchronized the source and target. This point marks the end of the change stream, or current end-of-log (EOL), if you stop update activity on the source, as recommended, until after target materialization and restart token generation are complete.

On z/OS, the sequence tokens have the same length for all source types.

If you use PowerExchange Condense with Full condense processing, PowerExchange uses the sequence token to determine the point from which to start reading change data from condense files, and uses the restart token to verify that the source instance is correct for the starting change record. The sequence token represents the full condense file and the position of the change record in that file. The restart token contains the source instance name from the registration group.

To create restart tokens for the current EOL, use one the following methods:

PWXPC restart token file: To generate current restart tokens for a CDC session that uses real-time or continuous extraction mode, specify the CURRENT_RESTART option on the RESTART1 and RESTART2 special override statements in the PWXPC restart token file. When the CDC session runs, PWXPC requests that PowerExchange provide restart tokens for the current EOL. PWXPC uses the restart information to locate the extraction start point.
Database row test: In the PowerExchange Navigator, perform a database row test with a SELECT CURRENT_RESTART SQL statement.
DTLUAPPL utility: Run the DTLUAPPL utility with the GENERATE RSTKKN option.

If you use the DTLUAPPL utility or PowerExchange Navigator to generate restart tokens, enter the token values in the PWXPC restart token file before you start the CDC session.

You can also construct restart tokens by using the RBA or LRSN of an event mark record in the PowerExchange Logger log files. You can use the EDMXLUTL utility to generate event marks. Also, the following PowerExchange ECCRs for z/OS data sources generate event marks in the some situations:

The DB2 ECCR generates an event mark when it reads a quiesce point from the DB2 logs. DB2 creates quiesce points when you use the DB2 QUIESCE utility.

The IMS log-based ECCR generates an event mark when it reads records that the DTLCUIML utility created in the IMS logs.

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CDC Guide for z/OS

CDC Guide for z/OS

Creating Restart Tokens for Extractions

Creating Restart Tokens for Extractions