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Change Data Capture & Change Tracking Deep Dive

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Presentation on theme: "Change Data Capture & Change Tracking Deep Dive"— Presentation transcript:

1 Change Data Capture & Change Tracking Deep Dive
W. Kevin Hazzard 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

@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

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

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