Sensible values for Database Mirroring Monitor Threshold

  • Kwisatz78

    SSChampion

    Points: 12478

    Hi all

    As the title suggests I am wondering what other people are using as thresholds for database mirroing. We have a multi-site mirror which is connected by fibre cable roughly 100 yards away, and the system is low transactional.

    With that in mind what do people consider a sensible threshold for unsent log, unrestored log, oldest unsent transaction and mirror commit overhead?

    Thanks for your suggestions.

  • Perry Whittle

    SSC Guru

    Points: 233771

    Kwisatz78 (10/8/2012)


    Hi all

    As the title suggests I am wondering what other people are using as thresholds for database mirroing. We have a multi-site mirror which is connected by fibre cable roughly 100 yards away, and the system is low transactional.

    With that in mind what do people consider a sensible threshold for unsent log, unrestored log, oldest unsent transaction and mirror commit overhead?

    Thanks for your suggestions.

    Are you referring to the default timeout value?

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  • Kwisatz78

    SSChampion

    Points: 12478

    Hi Perry

    I am referring to the thresholds you can set in the Database Mirroring Monitor itself, which I want to configure SCOM to alert on. Table 1 in the following link shows the event IDs, but I was just wondering what values are sensible to use for these thresholds.

    http://technet.microsoft.com/en-us/library/cc966392.aspx

    Thanks

  • Jack 95169

    SSC-Addicted

    Points: 401

    I've been wondering myself - since mirroring is now deprecated in favour of Always On, I think it is a minority sport these days
    Microsoft sets these defaults - 
    Unsent log exceeds 1KB
    Unrestored log exceeds 1KB
    Oldest unsent transaction exceeds 1 minute
    Mirror commit overhead exceeds 1millisecond

    I would recommend starting with these and seeing how it goes.  

    Remember to go to the SQL Agent jobs - find Database Mirroring Monitor Job - and set it to Notify you if it finds a problem

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