Understanding ASYNC_NETWORK_IO Waits in SQL Server

In SQL Server, ASYNC_NETWORK_IO wait time can be high due to slow network, like when the database is in the cloud and the application is on premise. Furthermore, it can be slow when CPU utilization is high in the application server preventing timely fetching of all rows or, in most cases, when the application reads a row, does some work processing the row, before reading the next row. When the server sends data, the ASYNC_NETWORK_IO wait time will not increase beyond 2000ms. After 2000ms the server will increase the wait count and reset the wait time, which is demonstrated in the video.

The below video covers ASYNC_NETWORK_IO waits while the server is sending data to the client. The video suggests ways to identify slow network and discusses high ASYNC_NETWORK_IO wait time and guidelines to reduce the waits. SQLTest Tool simulates the hands-on labs for you, no registration necessary. You can practice the online hands-on example while watching the video.

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