So I am trying to configure a two server setup, both containing SQL with independent storage. We're using windows server 2012, and I have a question about mirroring. If the server's data bases are in sync then the primary server fails and the mirrored server takes over. How do I re-synchronize the servers after I put the primary(now the one that will act as the mirror) back up? Is that handled automatically?

Edit: I guess I mean after a fail over, how does the old primary get back in sync with the mirror that has been receiving transactions. I think the endpoints are crucial as Kin said.

  • Mario, are you using automatic failover?
    – QWE
    Jun 30, 2016 at 15:28
  • @QWE nope, we're using manual failover (maybe forced manual failover) Jun 30, 2016 at 15:30
  • 1
    If you run this on your mirror server (which became primary after failover) then your servers will be back to their original roles. 'ALTER DATABASE [yourDatabase] SET PARTNER FAILOVER GO' Please have a look: link
    – QWE
    Jun 30, 2016 at 15:36
  • Also this one: sqlservercentral.com/blogs/robert_davis/2009/02/22/…
    – QWE
    Jun 30, 2016 at 15:46

1 Answer 1


When you do a failover, a role reversal happens i.e. your primary becomes secondary and your secondary becomes primary.

ALTER DATABASE [yourDatabase]

Doing so, only the role reversal happens (this is what happens when you initiate a failover using above command) and mirroring direction is reversed - principal becomes mirror and vice-versa. Note that MIRRORING is not BROKEN. Refer to my answer : If I fail over one database, do the others that share the same mirror endpoint fail over as well? for more details.

You can have your application use Failover Partner=your_mirror_serve_name, so that your application is redirected to replica database when a failover happens.

Refer to : connectionstring in Database Mirror setup

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