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.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.Side-by-side upgrade will require the upgrade of subscriber to happen together with the publisher and requires a re-initialization of the subscribers. 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.) 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 : 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.Installation of the Cumulative Update is similar to the installation of a Service Pack.Cumulative Updates are not fully regression tested.* Since January 27, 2016: Microsoft recommends ongoing, proactive installation of SQL Server CUs as they become available.
The requirements of upgrading a replication topology need to abide by the following guidelines: 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.
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.
You need to speed up a SQL Server app, but you only want to make index changes.
You don’t want to buy hardware, change SQL Server, or change the code.