CDC Guide for Linux, UNIX, and Windows

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DDL-Updated Catalog of MySQL Source Table Definitions

PowerExchange uses a catalog in a MySQL database to store MySQL source table definitions. When PowerExchange detects a DDL change of CDC interest to a source table, PowerExchange updates the source table definition in the catalog. The catalog of updated source table definitions helps PowerExchange avoid errors when reading change data for a DDL-updated table.

PowerExchange updates the source table definitions in the catalog only for DDL change events that affect CDC. Typically, these DDL changes are those that require you to re-create or modify the capture registrations and extraction maps for the source tables, for example, column add, drop, or rename operations and table drop or rename operations.

To prepare for catalog use, perform the following tasks:

Create the catalog tables, PWXCatTables and PWXCatUpdates, on a Linux or Windows system. The tables can be in the MySQL source database or in another local or remote MySQL database. Use the PWXCATMY utility.

A single catalog can record MySQL source table definitions for multiple PowerExchange registration-group instances.

Verify that the catalog tables have the correct format. Use the PWXCATMY utility.

Check that an active capture registration exists for each source table.

Create a snapshot of the source table definitions and record the snapshot information in the catalog. The snapshot provides the baseline table definitions that will be updated by subsequent DDL changes. Use the PWXCATMY utility.

In the DBMOVER configuration file, edit the MySQL CAPI_CONNECTION statement to specify the schema of the catalog tables in the CATSCHEMA parameter. Optionally, you can also specify catalog connection parameters. These parameters will be used during change capture processing.

With the PWXCATMY utility, you can perform all of the following catalog-related tasks:

Create the catalog tables.

Show the DDL statements for creating the catalog tables.

Verify that the catalog tables have the correct format.

Create a snapshot of the source table definitions and write that information to the catalog.

Remove, or unregister
, source table definitions from the catalog.

List the source table names for which table definitions exist in the catalog.

Dump the source table definitions that are recorded in the catalog.

Drop the catalog tables.

For more information about the PWXCATMY utility, see the

PowerExchange Utilities Guide

After the catalog is configured, keep in mind the following usage considerations:

If you rename a registered table from which change data was captured and then switch back to the original table name, the second rename event is not recorded in the catalog.

If you change the NOT NULL option of a registered source column to NULL, the source table becomes invalid and CDC processing ends. An attempt to warm start the CDC session will fail. However, if you change the NULL option to NOT NULL, the change is successfully recorded in the catalog and processing continues.

If you replace or rename the binlogs after configuring the catalog, such that the original binlogs are no longer in use, you must remove (unregister) the source table definitions from the catalog, re-create snapshots of the source table definitions in the catalog, and then cold start the CDC sessions. For more information, see Changing the Binary Log Location or Base Name.

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