Is it necessary to stop working on the database when preparing the mirroring process?

If I take an old backup of the main database and restore it, will all the new data be transferred when running mirroring?

How can witness server help me in case of automatic failure?


1 Answer 1

  1. The mirorring can be configured even if there is workload on the database.

  2. I am not sure I understand your question properly here. If you mean having a primary DB on the principal, restore (WITH NORECOVERY) on the mirror and configure mirroring while principal is still receiving workload, then the answer is YES, the changes done by workload will be re-played from principal on the mirror. If that's not the case, please clarify further what you meant.

  3. Witness is there to (besides others) prevent split-brain (having both principal and mirror active at the same time). From Microsoft: " If the partners become disconnected from each other, they rely on the witness to make sure that only one of them is currently serving the database"

However, as Mr. Browne has commented your post, you'd be better of with always on availability groups. It's a pity you aren't on something newer, from SQL2016, there are Basic always on availability groups.


  • 1
    To add to Sranda's answer, as long as you restored on the mirror server up to the last log backup taken on principal server, you'll be able to configure mirroring. Dec 6, 2021 at 19:52
  • As Microsoft states : ``` Note This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use Always On availability groups instead. ``` learn.microsoft.com/en-us/sql/database-engine/…
    – Hybris95
    Dec 7, 2021 at 15:19

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