1. Change Data Capture & Change Tracking Deep Dive
W. Kevin Hazzard
LinchpinPeople.com
Group Principal

2. Change Data Capture analysis transactions warehouse sources data mart
Turn it on EXECUTE sys.sp_cdc_enable_db;
Which generates for the whole database
A capture job
A cleanup job
Then include at least one table with EXECUTE sys.sp_cdc_enable_table …;
Which creates a capture instance containing
A change table
An all-changes function
A net-changes function (optional)
transactions
sources
data
mart
ETL
capture job
warehouse
ETL
archive
sector
changes

3. Capture Instance Contains Maximum two per source table
The capture table
cdc.fn_cdc_get_all_changes_<instance name> function
cdc.fn_cdc_get_net_changes_<instance name> function (optional)
Maximum two per source table

4. Sys.sp_CDC_ENABLE_TABLE
@source_schema
@source_name
@supports_net_changes
@role_name
@filegroup_name
@index_name
@captured_column_list
@allow_partition_switch
@capture_instance

5. DEMONSTRATION Enabling Change Data Capture (CDC)
Creating a CDC Capture Instance
Querying CDC Tables as Things Change

6. SQL Server Agent JOBS cdc.Capture_capture
Starts with SQL Agent
RAISERROR(22801, 10, -1);
EXEC sys.sp_MScdc_capture_job;
Just a wrapper for sys.sp_cdc_scan
cdc.Capture_cleanup
Runs at 02:00 daily
EXEC sys.sp_MScdc_cleanup_job;

7. CDC Data Retention Based on LSN Validity Intervals
Database
Capture Instance
The cleanup job deletes CDC data acording to retention policy SELECT * FROM msdb.dbo.cdc_jobs WHERE job_type = N'cleanup';
You can start the cleanup job manually EXEC = N'cleanup';

8. Handling Schema Changes
Deleted and new columns are handled well
Modified columns require specific steps:
Stop the capture and cleanup jobs
Change the schema as necessary
Generate new capture instances for all modified tables
Process all data in the old and new capture instances
Manually run the cleanup job
Delete the old capture instance
Turn the capture and cleanup jobs back on

9. Change Tracking transactions warehouse
Turn it on for one database ALTER DATABASE <DBNAME> SET CHANGE_TRACKING = ON;
Then enable a table ALTER TABLE <TBLNAME> ENABLE CHANGE_TRACKING;
sync
transactions
warehouse
ETL
sources
archive
sector

10. Change Tracking TABLES & FUNCTIONS
sys.change_tracking_databases
sys.change_tracking_tables
CHANGETABLE(CHANGES)
CHANGETABLE(VERSION)
CHANGE_TRACKING_CURRENT_VERSION()
CHANGE_TRACKING_MIN_VALID_VERSION()
CHANGE_TRACKING_IS_COLUMN_IN_MASK()
WITH CHANGE_TRACKING_CONTEXT

11. DEMONSTRATION Enabling Change Tracking (CT) for a Database
Enabling CT on a Table
Querying CT Tables and Functions as Things Change

12. Handling Schema Changes
No modifications to the primary key are allowed including related indexes
Dropping columns is OK but they may still appear in the change data
When adding columns, changes are tracked but the metadata change is not reported
Switching partitions will fail on change tracked changes
Data type changes are not tracked

13. Which one is RIGHT FOR ME?
Change Data Capture
Change Tracking
Works in Enterprise Edition only
Stores every discrete change
Storage intensive
Good for auditing
Requires SQL Server agent
No special serialization required
Works in all versions of SQL Server
Returns differences from current
Storage light
Good for device synchronization
No job agent required
Operates best with snapshot isolation