SQL Mirroring Port could stop working unexpectedly

When it comes to diagnosing and fixing some SQL Mirroring issues we may have to face with bizarre causes that could stop working a database mirroring and as a result the state of it will be "disconnected". For instance, one of the most common problems is that the SQL mirroring port may stop working unexpectedly. Consequently, the whole database mirroring functionality will stop working too. We basically configure SQL Server mirroring to use the port 5022 by default which works good enough for the vast majority of cases. To be perfectly honest, there is not an urgent need to change it since the issue is not about the port number (or mirroring configuration) but the port itself.

While working on fixing the issue, we may think the database mirroring port may have stopped working or blocked for some security reason which we do not know accurately at the beginning of the situation. Nevertheless, the reason should be investigated further by the Network team so as to prevent from getting the same issue in the future again. Having clear the situation, I am going to show one way to have the database mirroring working again. To begin with, we need to figure out what is the current number port of the mirroring being used.



We can see that the mirroring port is 5022, so we can opt to change it.

ALTER ENDPOINT [Mirroring] AS TCP (LISTENER_PORT = 5023)

Only after successfully completing that will we have to restart the database engine. Finally, we need to restore the original port and then restart again the database engine.

ALTER ENDPOINT [Mirroring] AS TCP (LISTENER_PORT = 5022)

Having done it, we will see the database mirroring working properly. That's is all for now. I hope this tip also works for you. Let me know any remarks you may have. Thanks for reading.