Wednesday, 20 December 2017

Always On: Trying out Read-Only intent connections to secondary replicas

SQL Server Always On Availability Group enables us to connect Read-Only workloads to secondary replicas automatically by using differents ways. For instance, to connect .NET applications to secondary replicas, we must also include "ApplicationIntent=ReadOnly" besides the AG Listener Virtual Name in the connection string. More specifically, after configuring the Read-Only Routing list, this would be the connection string if we had an Availability Group with a Listener called "AGLISTENER" (in these examples it is used Windows Authentication).


But that is not all, it is also possible to establish connection to secondary replicas via SQLCMD tool by using the new parameter -K (and optionally -M for faster detection of and connection to the active server). If -K is not specified, the sqlcmd utility will not support connectivity to a secondary replica. So, this would be a simple example of how to use SQLCMD with -K and -M parameters. I couldn't have been simpler.

Sqlcmd -S AGLISTENER  -E  -K ReadOnly -M

And last but not least, we can also do it by using SSMS Connection Dialog window by using “ApplicationIntent=ReadOnly” in the "Additional Connection Parameter" tab. I also wrote another post about it with more details, take a look at it.

To sum up, these are the basic ways to try out Read-Only intent connections to secondary replicas, the first way is ideal for developers whereas the second and third if you are working as a DBA.
That is all for now. Let me know any remarks you may have. Stay tuned.

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