CDC Guide for Linux, UNIX, and Windows

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PostgreSQL CDC Considerations

Review the following operational considerations for PostgreSQL CDC.

For registered PostgreSQL source tables, PowerExchange captures DML changes (inserts, updates, and deletes) but does not capture DDL changes.

Each PostgreSQL source table must have a primary key before it can be registered for CDC.

For PostgreSQL CDC, use of the PowerExchange Logger for Linux, UNIX, and Windows is optional.

The PowerExchange Logger reads capture registrations for PostgreSQL sources only when it starts. If you change the registrations while the PowerExchange Logger is running, you can warm start the Logger and the changes will take effect.

The replication store can grow large in size unless you take one of the following actions:

Specify ENABLELWM=Y in the PG CAPI_CONNECTION statement. With this setting, change data that has been hardened to PowerExchange Logger log files will be deleted from the replication store table automatically. To retain the table data longer, you can back up the replication store table.

Manually delete data from the replication store table by using the following SQL command:

DELETE FROM store_table_name [WHERE condition]

If you omit the WHERE clause, all table rows are deleted.

You might need to take some action if the following DDL changes are made to registered source tables:

If you drop a registered source table, no action is required because no DML changes will be captured for the dropped table. However, you might want to remove the associated capture registration, which is no longer needed.

If you add columns to a source table, PowerExchange continues CDC processing but no data from the new columns is processed. To process data from these columns, you must re-create the capture registration for the source table and then warm start the CDC session.

If you delete columns that are included in the capture registration for a source table, PowerExchange issues an error message and the session stops. You must re-create the capture registration without selecting the columns and then warm start the CDC session.

If you stop the CDC session, change data continues to be cached on the PostgreSQL server in the pg_xlog file. To avoid errors, make sure that the pg_xlog file does not become full.

PowerExchange does not support EnterpriseDB (EDB) PostgreSQL.

PowerExchange uses the DataDirect ODBC driver for PostgreSQL to connect to PostgreSQL source databases. You can define the ODBC_CONN_PARAMS statement in the dbmover.cfg file If you want to add ODBC parameters to the connection strings that are used on the servers you specify for the following processing:

Change data capture

Creating, deleting, or modifying capture registrations from the PowerExchange Navigator or DBLUCBRG utility

For example, you might need to add ODBC parameters if your site policies require database connections to use SSL encryption, specific cryptographic protocols, or self-signed or third-party signed SSL certificates. For more information, see the PowerExchange Reference Manual
.

PostgreSQL CDC only returns accurate before-image values on UPDATE and DELETE operations for key columns. All non-key columns report a NULL value. To replicate the before-image (BI) and change-indicator (CI) values, alter the table by using an

ALTER TABLE <tblname> REPLICA IDENTITY FULL

statement.

PostgreSQL CDC

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