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what are the possible causes/Scenarios does always on failover?

  • September 11, 2015 at 8:48 am

    #303070

    I have setup always on availability groups between 2 stand alone SQL servers, Automatic failover(Synchronous) in which 2 instances have WSFC enabled .

    what are the possible causes does always on failover?

    Possibilities i am aware of

    1.Disk filled out

    2.restart of instance/server

    3.upgrade or patch failed and cant connect to sql server

    4.Network cable pulled out

    like above what are other possible scenarios does always on failover?

  • September 14, 2015 at 5:02 am

    #1826314

    Hi,

    SQL Server AG or FCI executes a stored procedure sp_server_diagnostics that will return four event level messages (Clean, Warning, Error, Unknowns) from five component families:

    system

    resource

    query_processing

    io_subsystem

    events

    sp_server_diagnostics (Transact-SQL)

    https://msdn.microsoft.com/en-us/library/ff878233.aspx

    Then, depending on the fail over condition you set on your AG it will trigger or not the failover.

    Flexible Failover Policy for Automatic Failover of an Availability Group (SQL Server)

    https://msdn.microsoft.com/en-us/library/hh710061.aspx

    Crossing the component families, the event message levels and failover policy, you will be able of figuring out the types of scenarios will cause failover.

    Best regards,

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