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ASYNC_NETWORK_IO

Short Description

Occurs on network writes when the task is blocked behind the network. Verify that the client is processing data from the server.

Detailed Description

Occurs on network writes when the task is blocked waiting for the client application to acknowledge it has processed all the data sent to it. Verify that the client is processing data from the server or, less commonly-occurring, that network is performing as expected.

Reasons the client cannot consume data fast enough include:

application design issues like writing results to a file while the results arrive

waiting for user input, or an artificial wait introduced.

Also the client system may be experiencing slow response due to issues like low virtual/physical memory, 100% CPU consumption, etc. Network delays can also lead to this wait.

How to reduce this wait

Check the client side machine to ensure it is not short of resources making it unable to consume data quickly enough. Once this is established, check for network contention slowing the server to client data flow down.

Microsoft Docs - sys.dm_os_wait_stats (Transact-SQL)

SQL Skills - ASYNC_NETWORK_IO

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