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Troubleshoot the Change data capture resource in Azure Data Factory

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APPLIES TO: Azure Data Factory Azure Synapse Analytics

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This article provides suggestions on how to troubleshoot common problems with the change data capture resource in Azure Data Factory.

Issue: Trouble enabling native CDC in my SQL source.

For sources in SQL, two sets of tables are available: tables with native SQL CDC enabled and tables with time-based incremental columns.

Follow these steps to configure native CDC for a specific source table in your SQL database.

Consider you have following table, with ID as the Primary Key. If a Primary Key is present in the schema, supports_net_changes is set to true by default. If not, configure it using the script in Query 3.

Query 1


CREATE TABLE Persons (
	ID int,
	LastName varchar(255) NOT NULL,
	FirstName varchar(255),
	Age int,
	Last_login DATETIME,
    	PRIMARY KEY (ID));

Note

Currently the ADF CDC resource only loads net changes for insert, update and delete operations.

To enable CDC at the database level, execute the following query:

Query 2

EXEC sys.sp_cdc_enable_db

To enable CDC at the table level, execute the following query:

Query 3

EXEC sys.sp_cdc_enable_table  
	@source_schema = N'dbo'  
	, @source_name = N'Persons'  
	, @role_name = N'cdc_admin'  
	, @supports_net_changes = 1
        , @captured_column_list = N'ID';

Issue: Tables are unavailable to select in the CDC resource configuration process.

If your SQL source doesn't have SQL Server CDC with net_changed enabled or doesn't have any time-based incremental columns, then the tables in your source will be unavailable for selection.

Issue: The debug cluster isn't available from a warm pool.

The debug cluster isn't available from a warm pool. There will be a wait time in the order of 1+ minutes.

Issue: Trouble in tracking delete operations.

Currently CDC resource supports delete operations for following sink types - Azure SQL Database & Delta. To achieve this in the column mapping page, select keys column that can be used to determine if a row from the source matches a row from the sink. 

Issue: My CDC resource fails when target SQL table has identity columns.

Getting following error on running a CDC when your target sink table has identity columns,

Can't insert explicit value for identity column in table 'TableName' when IDENTITY_INSERT is set to OFF.

Run the following query to determine if you have an identity column in your SQL based target.

Query 4

SELECT * 
FROM sys.identity_columns 
WHERE OBJECT_NAME(object_id) = 'TableName'

To resolve this user can follow either of these steps:

  1. Set IDENTITY_INSERT to ON by running following query at database level and rerun the CDC Mapper

Query 5

SET IDENTITY_INSERT dbo.TableName ON;

(Or)

  1. User can remove the specific identity column from mapping while performing inserts.

Issue: Trouble using Self-hosted integration runtime.

Currently, Self-hosted integration runtime isn't supported in the CDC resource. If trying to connect to an on-premise source, use Azure integration runtime with managed virtual network.

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