When you resume database mirroring

  • In SQL Server 2008, if database mirroring breaks for some reason, and you want to resume mirroring with the principal again taking on the role of the principal after the mirroring temporarily served as principal, do you need to go back to square one? Meaning do you need to do full backup and t-log backup of the principal database and restore it on the mirror with no recovery? Or can you just run the below on the principal without without going back to square one:

    Use Master;

    GO

    Alter Database MyDB Set Partner Resume;

    I belive going back to square on would not be needed, and above command or simply click Resume in Database Properties > Mirroring Page.

  • It depends on what has happened on the principal after mirroring has been stopped. If you have a continuous log chain, then all you need to do is apply the transaction log backups to the mirror and restart mirroring.

    If the log chain is broken, you have to reinitialize with a new backup and restore.

    If the mirror is brought online, again - you have to start from the beginning again.

    Jeffrey Williams
    “We are all faced with a series of great opportunities brilliantly disguised as impossible situations.”

    ― Charles R. Swindoll

    How to post questions to get better answers faster
    Managing Transaction Logs

  • Hi Mr. Williams,

    You said if the mirror is brought online, I have start over. Do you mean if the mirror becomes a new principal via manual or automatic fail-over, and when I'm ready to fail-back to the original primary, then I will have to remove the mirroring, and reinitialize with the backup of the mirror (since it was promoted as the primary) and restore to the original primary? Is that correct?

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