latency observed from application to connect SQL Server in Azure

  • can some body else advise what parameter to check if there is high latency observed while connecting from application to SQL Server. As we recently migration on prime SQL Server to Azure VM SQL Server. Now the app team reporting there is high latency to connect DB for Azure IaaS SQL.

    Thanks,

  • That's a measure you have to do from the client. Azure SQL Database isn't going to see latency on it's end. It's going to get a connection request (however long it took to get there) and process it. You can look for wait statistics that indicate network & communication slow downs, but they're still not going to tell you much. That's purely a client side issue, whether the client is in Azure or local.

    ----------------------------------------------------
    The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood...
    Theodore Roosevelt

    The Scary DBA
    Author of: SQL Server 2017 Query Performance Tuning, 5th Edition and SQL Server Execution Plans, 3rd Edition
    Product Evangelist for Red Gate Software

  • thanks Grant your quick response and please share me query to check wait stats that will identify the network slowness. I can understand this purely from client side and client is in Azure only.

  • What is the client in Azure? What service?  Are they in the same region?  Are they in the same zone?  Are they in a proximity group?

    You will need to check that the vNet or the Service has access to the Microsoft.SQL.Database (iirc) network service in Azure otherwise it will be routing out via the internet to come back in, instead of using the Azure backplane.

    Azure SQL DB will not see any network latency on the connection, you will need to use something like Wireshark, to capture a packet trace between the client and the SQL DB endpoint

  • You can look at sys.dm_db_wait_stats, note, NOT sys.dm_os_wait_stats, to see network waits from the Azure SQL Database side of things. However, otherwise, you have to measure that from the client.

    ----------------------------------------------------
    The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood...
    Theodore Roosevelt

    The Scary DBA
    Author of: SQL Server 2017 Query Performance Tuning, 5th Edition and SQL Server Execution Plans, 3rd Edition
    Product Evangelist for Red Gate Software

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