How do I modify session timeout on a replica for a Distributed Availability Group?

Question

I have a Distributed Availability Group in my production environment that occasionally has a timeout.

When it does I get the following message in the AlwaysOn_health on the forwarder:

A connection timeout has occurred while attempting to establish a connection to availability replica 'xxx' with id [xxx]. Either a networking or firewall issue exists, or the endpoint address provided for the replica is not the database mirroring endpoint of the host server instance.

I wanted to try upping the connection timeout; it's currently set to the default of 10 seconds. I tried the following on the primary

USE [master]
GO
ALTER AVAILABILITY GROUP [xxx]
MODIFY REPLICA ON N'xxx' WITH (SESSION_TIMEOUT = 30)
GO

Since this is distributed, the replica is the underlying AG.

Running this I get the error: Cannot alter the availability group 'xxx', because it does not exist or you do not have permission.

I also tried on the forwarder, got the same error.

I am sysadmin, and the distributed AG shows up in sys.availability_groups, so it does exist and I do have permission.

How do I get around this error and modify session timeout on a replica for a Distributed Availability Group?

Answer 1

You want to alter the Distributed Availability Group and also Modify the Availability Group which is acting as a replica in the Distributed Availability Group. It's not intuitive nor is Docs forthcoming with any of that information.

Example:

ALTER AVAILABILTY GROUP [DistributedAGNameHere]
MODIFY AVAILABILITY GROUP ON 'AGNameUnderDistributedAG'
WITH (SESSION_TIMEOUT = 30)