This slide deck covers some of the important considerations around managing common maintenance tasks when using Always On Availability Groups in Microsoft SQL Server.

1. ALWAYSON AVAILABILITY GROUP
MAINTENANCE OPERATIONS
Things you need to consider.

2. Tuning blog: http://www.sqlperformance.com/
E-mail ebooks@sqlsentry.com for free copies of our $10 e-books:

3. YOUR PRESENTER
• John Q Martin
o Sales Engineer for SQL Sentry
o Worked with SQL Server for ~10 years
o Consultant, SQL DBA, Dev & BI Developer
o Former Microsoft Premier Field Engineer
• Contact Information
o Email: Jmartin@SQLSentry.com
o Twitter: @SQLServerMonkey
o LinkedIn: https://uk.linkedin.com/in/johnqmartin
o Arrange a Demo: http://www.meetme.so/JohnQMartin

4. AGENDA
• Introductions
• Maintenance Operations:
o Synchronizing Logins
o Statistics Maintenance
o Database Consistency Checks
o Database Index Maintenance
o Synchronizing SQL Agent Jobs
• Summary
• Wrap Up

5. WHAT & WHY?
• SQL Server Maintenance Operations
• Impact of using AlwaysOn Availability Groups on common
maintenance tasks.
• New maintenance tasks that you need to implement.

6. SYNCHRONIZE LOGINS
• Logins need to be synchronized between servers for Database
Replicas
• Windows Logins
o SID and other details from Active Directory
o Simple create login statement
• SQL Logins
o Need SID and Password Hash from server where database originated.

7. SYNCHRONIZE LOGINS
• Important to define synch process between replicas
o Downstream from primary or from where the change was made?
o How to handle conflicts?
• Options
o Manually
o SSIS package
o PoSh
o T-SQL
o Custom process

8. DEMO
Synchronizing SQL Server Logins between Availability Group Replicas.

9. TEMPORARY STATS
• When using Active Secondaries, statistics are created in TempDB
on the secondary replicas.
o Database is exact replica so cannot have stats created in it
o Workload is typically different to that of the primary
• Temporary Statistics will be lost on a SQL Server service restart.

10. TEMPORARY STATS
• New Maintenance job that we have not encountered before
o Identify and collect details of temporary statistics on active secondary
o Process for applying to primary replica
• Automated processing
o ! Caution ! Do not apply all temp stats to primary
o Gather to a location and review, approve for deployment

11. DEMO
Gathering and assessing Temporary Statistics.

12. DATABASE CONSISTENCY CHECKS
• Important to understand that DBCC CHECKDB() needs to be run
on all replicas.
o Each system has a unique storage platform that could have corruption
• Consistency Checks are part of corruption detection
o Use CHECKSUM page verification on databases
o Monitor for 823, 824, 825 errors
o DBCC CHECKDB()
• Important to make sure you monitor & manage
dbo.suspect_pages in MSDB

13. DATABASE CONSISTENCY CHECKS
• Automatic Page Repair can only do so much
o Will not repair File Header (Page 0)
o Will not repair Boot Page (Page 9)
o Will not repair GMA/SGMA/PFS pages
• Have a process for handling the detection of corruption.
o Script/Automate failover to a Secondary Replica in the event of a failed DBCC CHECKDB()
o Manual intervention
• Important to remember you cannot prevent corruption, but you
can plan for it.

14. DATABASE CONSISTENCY CHECKS
• Secondary needs to be active (readable) for the CHECKDB to
complete without errors.
o An alternative is to create a snapshot on the Secondary Replica and execute CHECKDB
against that.
• Be wary of the impact this will have on the primary if the IO
subsystem is shared.
o Heavy IO Load on the data volumes can result in disk latency if using shared controllers
or HBAs for storage access.

15. RE-INDEXING OPERATIONS
• AlwaysOn Availability Group Databases are in Full Recovery
Model – Fully Logged
o Generation of transaction log can be high
o Online Index Operations can have a very high impact
• Important to use an intelligent re-indexing mechanism
o Target only those that need to be re-indexed not all
o Use thresholds for reorganization and rebuild
• When is this operation taking place?
o Can impact RPO & RTO in the event of failover scenarios due to the amount of log
generated
o Do you have exclusive access to the database

16. RE-INDEXING OPERATIONS
• Can you make use of Asynchronous log transfer?
o Log throughput can artificially throttle the re-indexing process with synchronous transfer.
o This will remove the ability to leverage auto-failover while the operation is completing and
as the replica becomes synchronized.
Set all replicas
to
Asynchronous
Begin Re-
indexing
process
Return replicas
to prior state
(Sync/Async)
Verify replicas
are
synchronized

17. RE-INDEXING OPERATIONS
• What about suspending log transfer?
o Suspend data movement between replicas.
o Bypasses the performance restrictions on transaction log throughput.
Suspend Data
Movement on
Primary
Begin Re-
indexing
process
Resume Data
Movement on
Primary
Verify log is sent
and replicas
have caught up.

18. DEMO
Re-indexing operations with AlwaysOn Availability Groups

19. SYNCHRONIZE JOBS
• Important to understand job execution
o Execution on primary or secondary
o Logic in the job or master process to enable/disable
• Which jobs need to be synchronized
o Make use of custom categories to help identify jobs
• Important to define synch process between replicas
o Downstream from primary or from where the change was made?
o How to handle conflicts?

20. SYNCHRONIZE JOBS
• Conflict detection is important
o Job Configuration Options
o Job Step configuration
o Job Step body
• Methods of conflict detection
o Hash comparison
o String comparison
o Value comparisons

21. SYNCHRONIZE JOBS
• Jobs can have a lot of dependencies
o Proxies, Credentials, Operators
o Schedules, Categories, Output Locations
• Options
o Manually
o SSIS package
o PoSh
o T-SQL
o Custom process
o MSX Server

22. SUMMARY
• Think about the logic behind the synchronization of logins & jobs.
• How do you detect, review and handle conflicts between
synchronized objects?
• Consistency Checks (CHECKDB) needs to be done on all
replicas.
• Re-indexing is a balance between performance & impact to the
system.
• Materializing temporary statistics can improve system

23. QUESTIONS

24. THANK YOU!
• Slides will be available at http://blogs.sqlsentry.com
• More information at:
o SQLSkills, et al
• E-mail ebooks@sqlsentry.com for free copies of our e-books:
o Just tell them where you met me
• My contact info for other questions:
o Email: Jmartin@SQLSentry.com
o Twitter: @SQLServerMonkey