Upgrading a Replication Topology to SQL Server 2016


Cross posting from Tiger blog.

SQL Server Replication provides multi-faceted data movement capabilities across SQL Server releases which has been used by customers across the globe for a large number of years. When moving from one major release of SQL Server to another, replication topology upgrade has been a constant topic of lengthy discussions. In this post, we shall outline some of the challenges of upgrading SQL Server replication environments to SQL Server 2016. The requirements of upgrading a replication topology need to abide by the following guidelines:

  • A Distributor can be any version as long as it is greater than or equal to the Publisher version (in many cases the Distributor is the same instance as the Publisher).
  • A Publisher can be any version as long as it less than or equal to the Distributor version.
  • Subscriber version depends on the type of publication:
    • A Subscriber to a transactional publication can be any version within two versions (n-2) of the Publisher version. For example: a SQL Server 2012 Publisher can have SQL Server 2014 and SQL Server 2016 Subscribers; and a SQL Server 2016 Publisher can have SQL Server 2014 and SQL Server 2012 Subscribers.
    • A Subscriber to a merge publication can be any version less than or equal to the Publisher version.

If you had to draw a support matrix for the major release versions for transactional and merge replication, the output would be the two tables shown below.

For the remainder of this post, transactional replication refers to Transactional Replication excluding heterogeneous replication, P2P replication and updateable subscribers.

Transactional Replication Matrix

Publisher Distributor Subscriber
SQL Server 2016 SQL Server 2016 SQL Server 2016SQL Server 2014

SQL Server 2012

SQL Server 2014 SQL Server 2016SQL Server 2014 SQL Server 2016SQL Server 2014

SQL Server 2012

SQL Server 2008 R2

SQL Server 2008

SQL Server 2012 SQL Server 2016SQL Server 2014

SQL Server 2012

SQL Server 2016SQL Server 2014

SQL Server 2012

SQL Server 2008 R2

SQL Server 2008

SQL Server 2008 R2SQL Server 2008 SQL Server 2016SQL Server 2014

SQL Server 2012

SQL Server 2008 R2

SQL Server 2008

SQL Server 2014SQL Server 2012

SQL Server 2008 R2

SQL Server 2008

SQL Server 2005

SQL Server 2000

Merge Replication Support Matrix

Publisher Distributor Subscriber
SQL Server 2016 SQL Server 2016 SQL Server 2016SQL Server 2014

SQL Server 2012

SQL Server 2014 SQL Server 2016SQL Server 2014 SQL Server 2014SQL Server 2012

SQL Server 2008 R2

SQL Server 2008

SQL Server 2012 SQL Server 2012 SQL Server 2012SQL Server 2008 R2

SQL Server 2008

SQL Server 2008SQL Server 2008 R2 SQL Server 2008 R2SQL Server 2008 SQL Server 2008 R2SQL Server 2008

SQL Server 2005

SQL Server 2000

If you notice the line items for SQL Server 2016, you will see that a topology is unable to support SQL Server 2016 in a number of scenarios when you are running SQL Server 2016 as a publisher. Replication topologies have three common deployment patterns as shown in the visio diagram below. The distributor could be on the publisher or subscriber or a remote distributor. We do come across different deployments of the publisher and subscriber which are a mix of standalone instances, SQL Server failover cluster instances or Always On Availability Group replica instances.

image

Depending on the deployment pattern, the upgrade path to SQL Server 2016 would be different. Let us explore the different possibilities. SQL Server offers two upgrade paths in general:

  • Side-by-side: This approach involves setting up a new parallel environment and moving the databases along with the associated instance level objects like logins, jobs etc. to the new environment.
  • In-place upgrade: With this approach, the SQL Server setup program upgrades the existing SQL Server installation by replacing the existing SQL Server bits with the SQL Server 2016 bits and then upgrades each of the system and user databases. For environments running SQL Server failover cluster instances or Always On Availability Groups, an in-place upgrade is combined with a rolling upgrade to minimize downtime.

The scenarios below apply to Transactional Replication (without P2P Replication, Queued Updating Subscription and Immediate Updating Subscription) and Merge Replication. The options below outline how a phased approach can be adopted for your replication topology upgrade so that you don’t have to upgrade all the SQL Server instances in one big upgrade operation.

A common approach that has been adopted for side-by-side upgrades of replication topologies is to move publisher-subscriber pairs in parts to the new side-by-side environment as opposed to a movement of the entire topology. This phased approach helps to control downtime and minimize the impact to a certain extent for the businesses dependent on replication.

Upgrading a Replication Topology with a Remote Distributor

Transactional Replication

Upgrading from

Distributor

Publisher/Subscriber

SQL Server 2014

SQL Server 2012

Step 1:

In-place upgrade (Can be upgraded due to n-2 support)

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology*

Step 2:

In-place upgrade (Can be upgraded due to n-2 support)

OR

Side-by-side upgrade of subscriber requires reinitialization of subscriber

Side-by-side upgrade of publisher requires reconfiguring all the publisher-subscriber pairs

The publisher and subscriber can be upgraded in any order

SQL Server 2008 R2

SQL Server 2008

Step 1:

In-place upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology*

Step 2:

In-place upgrade would need to occur for both publisher and subscriber at the same time as publisher and subscriber need to be within two major releases. A SQL Server 2008/R2 publisher/subscriber cannot have a SQL Server 2016 publisher/subscriber.

OR

Intermediate In-place upgrade to SQL Server 2012/2014 of publisher or subscriber

The other server in the publisher/subscriber pair can then be upgraded to SQL Server 2016

OR

Side-by-side upgrade will require the upgrade of publisher and subscriber to happen together and requires a re-setup of the publisher/subscriber pairs

*See “Side-by-side Upgrade of the Distributor without re-initialization” below

Merge Replication

Upgrading from

Distributor

Publisher

Subscriber

SQL Server 2014

SQL Server 2016

Step 1:

In-place upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology*

Step 2:

In-place upgrade

OR

Side-by-side upgrade of publisher requires reconfiguring all the publisher-subscriber pairs

Step 3:

In-place upgrade

OR

Side-by-side upgrade of subscriber requires reinitialization of subscriber

SQL Server 2008 R2

SQL Server 2008

Step 1:

In-place upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology*

Step 2:

In-place upgrade

OR

Side-by-side upgrade of publisher requires reconfiguring all the publisher-subscriber pairs. Needs to happen with the upgrade of the subscriber.

Step 3:

In-place upgrade

OR

Side-by-side upgrade of subscriber requires reinitialization of subscriber. Needs to happen with the upgrade of the publisher.

*See “Side-by-side Upgrade of the Distributor without re-initialization” below

Upgrading a Replication Topology with Publisher acting as the Distributor

Transactional Replication

Upgrading from

Publisher/Distributor

Subscriber

SQL Server 2014

SQL Server 2012

Step 1:

In-place upgrade (Can be upgraded due to n-2 support)

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology*

Step 2:

In-place upgrade (Can be upgraded due to n-2 support)

OR

Side-by-side upgrade of subscriber requires reinitialization of subscriber

SQL Server 2008 R2

SQL Server 2008

Step 1:

In-place upgrade (Requires subscriber to be upgraded because publisher and subscriber need to be within two major releases. A SQL Server 2016 publisher cannot have a SQL Server 2008/R2 subscriber.)

OR

Intermediate in-place upgrade to SQL Server 2012/2014 for the publisher which is acting as the distributor also

The subscriber can be upgrade to SQL Server 2016 post the intermediate publisher upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs served by this distributor in the replication topology. Needs to happen with the upgrade of the subscriber.

Step 2:

In-place upgrade would need to occur for both publisher and subscriber at the same time as publisher and subscriber need to be within two major releases. A SQL Server 2008/R2 publisher/subscriber cannot have a SQL Server 2016 publisher/subscriber.

OR

Intermediate In-place upgrade to SQL Server 2012/2014 of the publisher

The subscriber can then be upgraded to SQL Server 2016

OR

Side-by-side upgrade will require the upgrade of subscriber to happen together with the publisher and requires a re-initialization of the subscribers. Needs to happen with the upgrade of the publisher.

*See “Side-by-side Upgrade of the Distributor without re-initialization” below

Merge Replication

Upgrading from

Publisher/Distributor

Subscriber

SQL Server 2014

SQL Server 2016

Step 1:

In-place upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs served by this distributor in the replication topology*

Step 2:

In-place upgrade

OR

Side-by-side upgrade of subscriber requires reinitialization of subscriber

SQL Server 2008 R2

SQL Server 2008

Step 1:

In-place upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs served by this distributor in the replication topology. Needs to happen with the upgrade of the subscriber.

Step 2:

In-place upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology. Needs to happen with the upgrade of the publisher.

*See “Side-by-side Upgrade of the Distributor without re-initialization” below

Upgrading a Replication Topology with Subscriber acting as the Distributor

Transactional Replication

Upgrading from

Distributor/Subscriber

Publisher

SQL Server 2014

SQL Server 2012

Step 1:

In-place upgrade (Can be upgraded due to n-2 support)

OR

Side-by-side upgrade requires re-setup of publisher/subscriber pairs in the replication topology served by this distributor*

Step 2:

In-place upgrade (Can be upgraded due to n-2 support)

OR

Side-by-side upgrade of subscriber requires re-setup of all the publisher/subscriber pairs

SQL Server 2008 R2

SQL Server 2008

Step 1:

In-place upgrade (Requires publisher to be upgraded also because subscriber and publisher need to be within two major releases. A SQL Server 2008/R2 publisher cannot have a SQL Server 2016 subscriber.)

OR

Intermediate in-place upgrade to SQL Server 2012/2014 for the subscriber which is acting as the distributor also

The publisher can then be upgraded to SQL Server 2016 post this intermediate distributor upgrade

OR

Side-by-side upgrade of distributor/subscriber requires re-setup of all the publisher/subscriber pairs served by this distributor. Needs to happen with the upgrade of the publisher.

Step 2:

In-place upgrade would need to occur for both publisher and subscriber at the same time as publisher and subscriber need to be within two major releases. A SQL Server 2008/R2 publisher/subscriber cannot have a SQL Server 2016 publisher/subscriber.

OR

The publisher can then be upgraded to SQL Server 2016 (Requires

intermediate In-place upgrade to SQL Server 2012/2014 of the subscriber)

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology. Needs to happen with the upgrade of the distributor/subscriber.

*See “Side-by-side Upgrade of the Distributor without re-initialization” below

Merge Replication

Upgrading from

Distributor/Subscriber

Publisher

SQL Server 2014

SQL Server 2016

Step 1:

In-place upgrade

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology served by this distributor*. This also requires upgrade of the publisher as the publisher version has to be higher than the subscriber.

Step 2:

In-place upgrade

OR

Side-by-side upgrade of subscriber requires reinitialization of all publisher/subscriber pairs. Requires simultaneous upgrade of the subscriber because it is acting as the distributor.

SQL Server 2008 R2

SQL Server 2008

Step 1:

In-place upgrade (Requires simultaneous upgrade of the publisher)

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology. Requires simultaneous upgrade of the publisher.

Step 2:

In-place upgrade (Requires simultaneous upgrade of the subscriber acting as the distributor)

OR

Side-by-side upgrade requires re-setup of all the publisher/subscriber pairs in the replication topology. Requires simultaneous upgrade of the subscriber because it is acting as the distributor.

*See “Side-by-side Upgrade of the Distributor without re-initialization” below

Side-by-side Upgrade of the Distributor without re-initialization

If you are running your SQL Server instance to be upgraded on Windows Server 2008 or Windows Server 2008 R2, then you will need to perform a side-by-side upgrade of the distributor first to Windows Server 2012 R2 or Windows Server 2016 before upgrading to SQL Server 2016. The reason for this intermediate OS upgrade is that SQL Server 2016 cannot be installed on a Windows Server 2008/2008 R2 server. The side-by-side approach can also help reduce downtime if you are upgrading the hardware of the Windows Server hosting the distributor instance. Downtime of the publisher and subscriber can be reduced using SQL Server Failover Cluster instances or Always On Availability Groups.

The assumption here is that the edition of the SQL Server instance will not change and a failover cluster instance of SQL Server will be upgraded to a failover cluster instance where as a standalone instance will be upgraded to a standalone instance using the steps mentioned below.

Steps for side-by-side migration of the distributor to Windows Server 2012 R2

  • Setup a new failover cluster or standalone instance running the same major release, editionĀ and version as your distributor on Windows Server 2012 R2/2016 with a different windows cluster and SQL Server FCI name or standalone host name. You will need to keep the directory structure same as the old distributor to ensure that the replication agents executables, replication folders and database file paths are found at the same path on the new environment. This will reduce any post migration/upgrade steps required.
  • Make sure that the current synchronization is complete and post that shut down all the replication agents
  • Shut down the current SQL Server failover cluster instance or standalone instance running as the distributor. If this is a standalone instance of SQL Server, you will need to shutdown the Windows Server hostingĀ  the SQL Server instance to ensure that there is no conflict while renaming the server.
  • Remove the DNS entries for the old (current distributor instance) environment and the AD entries for the computer object for the SQL Server FCI
  • If this is a SQL Server Failover Cluster instance, rename the new SQL Server Failover Cluster instance name with the old virtual server name. If this is a standalone SQL Server instance, then rename the new standalone host with the old hostname.
  • Copy the database files from the previous instance using SAN redirection or storage copy or file copy
  • Bring the new SQL Server instance online
  • Restart all the replication agents and verify if the agents are running successfully
  • Validate if replication is working as expected

In-place upgrade to SQL Server 2016

  • Run in-place upgrade for SQL Server 2016 on the new cluster
  • If required, rebuild old nodes and add to the cluster to re-use existing hardware
  • Validate if replication is working fine

If you want to reduce the downtime, we recommend that you perform the side-by-side migration of the distributor as one activity and the in-place upgrade to SQL Server 2016 as another activity. This will allow you to take a phased approach, reduce risk and minimize downtime.

Summary

Upgrading a replication topology is a multi-step process. We recommend attempting an upgrade of a replica of your replication topology in a test environment before running the upgrade on the actual production environment. This will help iron out any operational documentation that is required for handling the upgrade smoothly without incurring expensive and long downtimes during the actual upgrade process. We have seen customers reduce downtime significantly with the use of Always On Availability Groups and/or SQL Server Failover Cluster Instances for their production environments while upgrading their replication topology. Additionally, we recommend taking backups of all the databases including MSDB, Master, Distribution database(s) and the user databases participating in replication before attempting the upgrade.

Resources

Recovering a Deleted Cluster Name Object (CNO) in a Windows Server 2008 Failover Cluster

Upgrade Replicated Databases

Supported Version and Edition Upgrades for SQL Server 2016

Hardware and Software Requirements for SQL Server 2016

SQL Server Upgrade

Rename a Computer that hosts a Standalone instance of SQL Server

Rename a SQL Server Virtual Server Name

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SQL Server 2016 Public Preview (CTP2) – Live Query Statistics


I have spent a lot of time at customer locations working on resolving SQL Server performance issues on business critical environments. This also involves helping customers understand how to track down the performance bottlenecks and the remediation steps that need to be taken to remove identified performance bottlenecks. This involves two kinds of troubleshooting: post-mortem analysis and troubleshooting the issue as and when it is happening! Yes, I am talking about live troubleshooting which is a scary thing to do on a production server.

So if you share my deep rooted passion for working on SQL Server performance issues, the Live Query Statistics feature in SQL Server 2016 CTP2 is definitely worth knowing more about!

The Live Query Statistics can be enabled in one of the following ways:

1. Using Management Studio

The screenshot below shows the button which enables the Live Query Statistics. This can be a very powerful tool to troubleshoot bad query performance while the query is actually executing. You actually get insights into the plan and which part of the plan is actually taking time while the query executes.

Live Query Stats button on toolbar

You get a host of information from the Live Query Statistics as seen in the screenshot below. You will be able to pin point the part of the plan which is the culprit because you will have the completion percentage statistics for each and every operator in the plan. The completed operators show you the efficient parts of the plan. Additionally, you also get the time spent in each operator which gives you statistics for identifying the most time consuming part of the plan. And what’s more, you even know how much of the query is completed. This is one of the most common questions that I used to receive from customers while troubleshooting long running queries: “How long will the query take to complete“? Well now, there is an answer!

image

2. Use Activity Monitor

A new grid has been added in Activity Monitor named “Active Expensive Queries” which allows you to right-click a query and click on the “Show Live Execution Plan” option. Live Query Stats button in Activity Monitor

However, the “Show Live Execution Plan” option will only be enabled if the application  or user:

  • Executes SET STATISTICS XML ON; or SET STATISTICS PROFILE ON; in the target session.

  • The query_post_execution_showplan extended event has been enabled. This is a server wide setting that enable live query statistics on all sessions

And if you are developer, then you can use this feature in conjunction with the Transact-SQL debugger and pin point slow parts of the execution plan while the query is running. A truly powerful way to write and optimize queries! The debugging experience is now enhanced as the live query plan can be used along with breakpoints! The screenshot below shows what the debugging experience would look like.

image

Do keep in mind that this feature is provided for troubleshooting/debugging slow running query scenarios and should not be kept enabled in production environments. There is a moderate performance impact for collecting and displaying the above mentioned statistics.

Reference:

Live Query Statistics
https://msdn.microsoft.com/en-us/library/dn831878.aspx 

Disclaimer: Some information in this topic is preview and subject to change in future releases. Preview information describes new features or changes to existing features in Microsoft SQL Server 2016 Community Technology Preview 2 (CTP2).

SQL Server 2016 Public Preview (CTP2) – Deploying to Azure VM


I had written a post earlier on deploying a SQL Server instance on a Azure Virtual Machine. Now that SQL Server 2016 CTP2 is out, let’s see how that looks on Azure. The wizard is the same as before but a new gallery option exists for deploying SQL Server 2016 CTP2. The catch is that any virtual machine created with this gallery image will expire on June 30th, 2016. The locations where this image can be deployed are East Asia, Southeast Asia, North Europe, West Europe, Central US, East US, East US 2 and South Central US. The gallery image gets provisioned with a single disk.

image

After the deployment is complete, you will need to enable connectivity for your SQL Server database engine as outlined in an earlier post of mine. What you get is the default instance of Database Engine, Analysis Services, Integration Services and Reporting Services. The deployment will not have the “PolyBase Query Service for External Data”. So if you are planning to test the PolyBase options in SQL Server 2016, then you will need to run the installation from the C:\SQLServer_13.0_Full folder. The other feature that is not available is the Distributed Replay. So, if you are planning to play around with these two features, then you would need to run the installer again.

Another feature which the gallery image does not use is the tempdb multiple file option setup parmater, “SQLTEMPDBFILECOUNT“. This is left at 1 so you will end up with the default tempdb configuration which you saw in the older releases. I would recommend using a virtual machine instance which has a SSD drive as the temporary drive so that you can use a SSD for testing out any intensive workload which requires either high tempdb usage or a local disk which supports high IOPs.

So now you have any option to play around with SQL Server 2016 CTP2 without having to hunt down a separate virtual machine or physical box in your environment.