How am I getting Network_IO wait

  • If I am doing a select * from <local table>, then how am I getting a wait type of "Async_Network_IO"?

  • ASYNC_NETWORK_IO usually doesn't mean that you are waiting on the network. It usually means that the application is processing the data one row at a time or simply doesn't acknowledge the receipt of data. Have a look at this blog on how to troubleshoot this wait type: http://blogs.msdn.com/b/joesack/archive/2009/01/09/troubleshooting-async-network-io-networkio.aspx



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  • SSMS uses row by row processing. You could see this wait type when you run a query in SSMS on the database server itself. Indeed there is no network involved then.

  • Keith Tate (5/8/2014)


    ASYNC_NETWORK_IO usually doesn't mean that you are waiting on the network. It usually means that the application is processing the data one row at a time or simply doesn't acknowledge the receipt of data. Have a look at this blog on how to troubleshoot this wait type: http://blogs.msdn.com/b/joesack/archive/2009/01/09/troubleshooting-async-network-io-networkio.aspx

    Thanks Kieth. I will look at the link this week... I can do a trace to get the plan, and see what it is doing once the big query is run (a lot of queries to temp are run by the program to pull everything together for the generation of the data view). It is a complex series of pre-queries and then the big one, with a lot of sub-queries built in.

  • Those waits aren't about how the query is written. They occur when SQL has results that it is waiting to send to the client application.

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