1. Monitoring Data Changes with Change Data Capture
Arie D. Jones (AJ)
Principal Technology Manager
Perpetual Technologies, Inc
Blog :
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Twitter: programmersedge
#45 Louisville

2. Arie Jones (AJ) 20 + years application development experience
10 + years database experience
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3. Agenda How does Change Data Capture work How to implement
How to get to the data
Sneaky Ninja DBA Tips

4. ?
How it Works
So how does this mysterious Change Data Capture work? Let‘s take a look at how the magic happens…..
That big question mark is editable – use whatever character you want!

5. Why use this? Gives you consistency Reduces programmatic overhead
Reduces computational overhead

6. How it all works! Database Source Tables Log File Change Tables
Capture Process
User Queries

7. ?
How to Implement
That’s awesome AJ but how to you get the thing working??
Let’s find out!
That big question mark is editable – use whatever character you want!

8. Your Pre-Flight Checklist
SQL Agent is on and set to Auto-Start
You or someone you know has SysAdmin privileges
CDC user does not exist in database
A CDC schema does not exist in database
You have a good cover story to explain how difficult the following process is to your manager/boss so as to strengthen your argument for a raise

9. Step #1 Enable on the instance
Use sp_cdc_enable_db_change_data_capture
Use sp_cdc_enable_db
You may double check in sys.databases
This you must have SysAdmin privileges for

10. Step #2 Wipe sweaty brow Enable CDC per table
Use sp_cdc_enable_table_change_data_capture
Use sp_cdc_enable_table
You can double check in sys.tables
You will notice 2 jobs having been created
1 = Get Stuff
2 = Cleanup Stuff

11. Sp_cdc_enable_table_change_data_capture
@source_schema
@source_name
@role_name
@capture_instance
@supports_net_changes
@index_name
@captured_column_list
@filegroup_name

12. Demo
Let’s look at this in action!

13. ?
How to Query the Data
Now, how do we get to the actual data that we are saving up?
That big question mark is editable – use whatever character you want!

14. Querying Data Super easy syntax TableName_CT
Will normally need system functions to get LSN
Sys.fn_cdc_map_time_to_lsn
Then will use one of 2 CDC query TVF
Cdc.fn_cdc_get_all_changes_<schema>_<table>
Cdc.fn_cdc_get_net_changes_<schema>_<table>

15. Sneaky Ninja DBA TIP #1!
ETL Processes!

16. Demo
Straight to a demo!

17. Sneaky Ninja DBA TIP #2!
data forensics

18. Who’s making changes?
You’ll notice in the CDC tables that there is no username…
2 Things you need to think about
How are the users accessing the system?
How much flexibility do you have to change things?

19. Easy way! ID Customer User Updated 1 Jane Good DBA 2 Steve
Evil Developer 3
Bob ID
Customer 1
Jane 2
Steve 3
Bob
Change Data Capture takes care of the rest!!

20. Sneaky Ninja DBA TIP #3!
Performance tuning!

21. Let me explain the process
Job
Sys.sp_MScdc_capture_job
No Parameters!
That’s CRAZY!
Sys.sp_cdc_scan
Hey wait!
Isn’t that used in transactional replication?
Sys.sp_replcmds

22. Demo
Let’s jump into some code!

23. So What’s a DBA to Do? @captured_column_list @supports_net_changes
Limit # of columns to only those you truly need
@supports_net_changes
Only use if you need net changes
Puts an additional nonclustered index on change table
@filegroup_name
If not specified then change table is placed in default filegroup

24. Performance Tips Storage Workload Watch your log space
Watch you log I/O
Make sure you know which file group you have things stored in
Workload
Reduce the number of columns to the minimum
Modify default scan parameters on BOTH the capture and cleanup jobs!

25. Thank You ! Questions and Answers Evaluation Sheets!
Be sure to check out my upcoming events!
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26. SQL Saturday #45 Louisville@
SQL Saturday # Louisville
Monitoring Data Changes with Change Data Capture
Arie Jones(AJ)
Twitter: programmersedge
Company: