A popular relational database management system, the SQL Server, frequently runs across different delays affecting performance. One such wait type that might impede query execution is ASYNC_NETWORK_IO. We’ll go into the specifics of ASYNC_NETWORK_ IO wait types in this post, looking at their background, causes of recurrence, benefits, drawbacks, and practical strategies to reduce them. In addition, we’ll respond to the top ten queries concerning ASYNC_NETWORK_ IO delays.
Table of Contents
Introduction
SQL Server aims to provide the best performance possible in the quick-paced world of database administration. Even well-optimized queries can, however, experience bottlenecks, and ASYNC_NETWORK_IO is frequently to blame. When a SQL Server session waits for a client application to consume query results, ASYNC_NETWORK_ IO wait types appear. As a result, users may experience slow query performance.
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Historical Background
For many years, SQL Server’s performance measurements have included the ASYNC_NETWORK_ IO wait type. Its origins may be traced back to the requirement for effective server-to-client synchronization during data transfer. Although SQL Server has improved over time at managing these lags, they can still be problematic, particularly when there is a high network latency or sluggish client applications.
Advantages of ASYNC_NETWORK_ IO Wait Type
A few advantages of ASYNC_NETWORK_ IO wait types are given below for more clarity & better understanding:
Non-Blocking Nature
Since ASYNC_NETWORK_ IO is non-blocking, it does not interfere with executing other queries. Since it enables SQL Server to manage several clients concurrently, this might be helpful in settings with many concurrent connections.
Concurrency
Thanks to ASYNC_NETWORK_ IO, SQL Server may handle concurrent client requests. When appropriately handled, this concurrency can increase database throughput and responsiveness.
Supports Asynchronous Processing
The ASYNC_NETWORK_IO flag on SQL Server indicates that it can execute queries asynchronously, which is helpful for programs that need responsive user interfaces and may keep running while awaiting data.
Disadvantages of ASYNC_NETWORK_ IO Wait Type
A few disadvantages of ASYNC_NETWORK_ IO wait types are given below for more clarity & better understanding:
Performance bottleneck
When clients take too long to obtain and analyze data delivered by SQL Server, ASYNC_NETWORK_ IO may become a performance bottleneck. This may lead to user discontent and slower query response times.
Resource Consumption
Using ASYNC_NETWORK_ IO to manage several concurrent connections might drain server resources like CPU and memory. When several connections are active at once, resource contention may occur, impacting system performance.
Increased Complexity
Managing asynchronous processing can be more difficult for developers, as they must ensure the application can handle data as it comes in rather than waiting for it to be entirely received.
Limited Control
The pace at which the client application processes data is not directly within SQL Server’s control. ASYNC_NETWORK_ IO waits may continue if the client is inefficiently handling data, and SQL Server has little influence over this situation.
Potential for Latency
ASYNC_NETWORK_ IO waits may occur more frequently in circumstances with significant network latency, which might result in decreased query performance. While SQL Server cannot always regulate this, it might nevertheless be a drawback in some situations.
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Why ASYNC_NETWORK_IO Wait Type Occurs
ASYNC_NETWORK_IO When a SQL Server session waits for a client application to use or process the server-sent data, this is known as a wait type in SQL Server. These delays frequently occur for the reasons listed below:
Slow-Performing Client Applications
Slow-performing client apps are one of the most frequent reasons for ASYNC_NETWORK_IO delays. A query’s result set is sent to the client for processing when the server has finished running the query. If the client application is sluggish in reading and processing data, the SQL Server session must wait until the client application has finished consuming it. ASYNC_NETWORK_IO waits represent this waiting period.
Network Latency
ASYNC_NETWORK_IO delays can be caused by high network latency between the SQL Server and the client. Latency arises when data transmission takes longer due to network congestion, sluggish connections, or physical distance between the server and client.
Large Result Sets
Large result sets from queries may also cause ASYNC_NETWORK_IO pauses. When SQL Server wants to send a sizable volume of data to a client, the transmission process takes some time. If the client is delayed in processing this enormous result set, ASYNC_NETWORK_IO delays happen.
Client-Side Processing Delays
ASYNC_NETWORK_ IO Waits could happen when the client application processes data from SQL Server slowly or runs into processing bottlenecks. This may occur if the client application processes the data resource-intensively, such as through intricate computations or transformations.
Inefficient Data Retrieval
ASYNC_NETWORK_IO delays may result from the client application retrieving data row by row rather than more quickly. This is especially true for cursor-based processing, which fetches each row separately.
Client Connection Pooling
When connection pooling is employed, ASYNC_NETWORK_IO waits may develop when connections are not effectively reused. The cost of setting up and pulling down connections might cause processing delays.
Client-Side Locks and Blocking
Data consumption may be delayed and result in ASYNC_NETWORK_IO delays if the client program retains locks or has blocking problems. When the client is still processing query results while attempting to update or alter data, this might happen.
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How to Avoid ASYNC_NETWORK_IO Wait Types
Optimizing many elements of your database system, application, and network settings is necessary to prevent or reduce ASYNC_NETWORK_IO wait types in SQL Server. Here are a few techniques to reduce ASYNC_NETWORK_IO waits:
Optimization of Client Application
Make sure the client programs are optimized to consume query results quickly. This involves processing data from SQL Server as soon as possible.
Optimizing a network
Reduce network latency by improving network infrastructure and parameters. Make sure your network connections are dependable and quick.
Question tuning
Limit the size of the result sets that queries return. Avoid retrieving extraneous data. Use effective pagination and filtering methods to minimize the quantity of data transmitted.
Compression
Use network data compression methods to reduce data transport times. Data compression, which can help minimize the amount of data for transmission, is supported by SQL Server for backup operations.
Batch Operation
If your application allows it, consider using batch processing, which combines several processes into a single transaction. Fewer individual transactions may result in fewer ASYNC_NETWORK_IO waits.
Pooling of Connections
Effectively configure connection pooling. To reduce the cost associated with regularly generating and destroying connections, make sure connections are reused wherever feasible.
Programming in asynchronous fashion
Integrate asynchronous programming approaches in your client application. By enabling non-blocking data retrieval and processing, ASYNC_NETWORK_ IO delays are minimized.
Improvement of Server Resources
Confirm that the SQL Server instance has enough CPU, memory, and disc I/O to efficiently manage a large number of connections. Conflicting resource demands might result in data processing delays.
Indexing and querying performance
Correctly indexing your tables will enhance query performance. Using well-designed indexes and rapid searches can also reduce the time needed to access and transfer data.
Monitoring and Profiling
Monitor ASYNC_NETWORK_ IO wait data and profile your application to identify performance bottlenecks. This can help uncover areas that need to be optimised.
Maintaining Databases
Perform routine database maintenance tasks, such as index rebuilding, statistics updating, and log file management, to keep your database working effectively.
Think about Delayed Durability
You might investigate SQL Server’s delayed durability feature, which can lessen log writing overhead if it is acceptable for your application’s data consistency needs.
Networking Enhancements
Identify and resolve any network bottlenecks or congestion that may be causing ASYNC_NETWORK_ IO delays by working with network administrators.
Throttling on the client side
Implement client-side controls to limit the frequency of server data requests. This can help prevent the client application from becoming overloaded.
Customer-Side Caching
Reduce the number of times the client application must retrieve data from the server by implementing caching methods.
Enhancing Data Processing
Analyse and improve the client application’s data processing logic. Find and fix any inefficiencies that could be behind the sluggish data usage.
Example of ASYNC_NETWORK_ IO Wait Type
The ASYNC_NETWORK_IO wait type in SQL Server usually means that the server is awaiting data consumption from the client. It may occur if the client needs help processing or receiving the data quickly enough after it is sent from the server. Large result sets, sluggish client processing, and network latency can all contribute to this.
Here’s an illustration of a T-SQL query scenario:
Making a test database & table to test, ASYNC_NETWORK_IO waits type:
--Script to create a database
CREATE DATABASE IMS;
GO
USE IMS;
GO
--script to create a sample table
CREATE TABLE Items(
ItemID INT PRIMARY KEY IDENTITY(1,1),
ItemName VARCHAR(50) NOT NULL,
ItemBasePrice decimal(10,2) NOT NULL,
ItemSalePrice decimal(10,2),
IsActive bit DEFAULT 1,
CreatedOn DateTime DEFAULT GETDATE()
);
GO
-- Script to insert a few sample data in the Items table
INSERT INTO Items(ItemName, ItemBasePrice)
SELECT TOP 1000000
'Item-' + CAST(ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS VARCHAR(50)),
ROUND(RAND(CHECKSUM(NEWID())) * (100), 2)
FROM sys.objects a
CROSS JOIN sys.objects b;
GO
--Script to update ItemSalePrice with ItemBasePrice + 15% extra
UPDATE Items
SET ItemSalePrice = ItemBasePrice+(ItemBasePrice*0.15)
GOExecuting a query that may cause ASYNC_NETWORK_IO waits.
-- A significant result set being sent to the client
SELECT * FROM Items
WHERE IsActve=1
GO
When running the query above, ASYNC_NETWORK_IO waits because the SQL Server will have to wait until the client is prepared to receive more data if the client application cannot process the data rapidly enough.
Finding ASYNC_NETWORK_IO waits type:
-- Script to validate ASYNC_NETWORK_IO wait statistics in SQL Server
SELECT @@ServerName AS [Server Name],
Getdate() AS [Current DateT ime],
wait_type AS [Wait Type],
wait_time_ms AS [Wait Time (In MS)],
waiting_tasks_count AS [Count Of Waiting Tasks]
FROM sys.dm_os_wait_stats
WHERE wait_type = 'ASYNC_NETWORK_IO';
GO
Utilizing ASYNC_NETWORK_IO waits to monitor active sessions:
-- Monitoring active sessions and respective wait types
SELECT @@ServerName AS [Server Name],
Getdate() AS [Current DateT ime],
session_id AS [SPID],
status AS [Status],
wait_type AS [Current DateT ime],
wait_time AS [Wait Type],
last_wait_type AS [Last Wait Type],
wait_resource AS [Wait Resource]
FROM sys.dm_exec_requests
WHERE wait_type = 'ASYNC_NETWORK_IO';
GO
Optimizing to lower wait times for ASYNC_NETWORK_IO:
Take into account the following tactics to lower ASYNC_NETWORK_IO wait times:
To fetch data in smaller portions, use pagination.
Make sure that the client application has adequate capacity to handle the data.
Reduce latency and increase network bandwidth.
Using pagination with OFFSET and FETCH, for instance:
-- Script to fetching the data in smaller size to avoid ASYNC_NETWORK_IO waits
DECLARE @PageNumber INT = 1;
DECLARE @PageSize INT = 10;
SELECT *
FROM Items
ORDER BY ItemID
OFFSET (@PageNumber - 1) * @PageSize ROWS
FETCH NEXT @PageSize ROWS ONLY;
GO
By comprehending and resolving the reasons behind ASYNC_NETWORK_IO waits, you can enhance the responsiveness of your client apps and the efficiency of your SQL Server database.
Conclusion
To maintain SQL Server performance, it is essential to comprehend and address ASYNC_NETWORK_ IO wait types. Optimizing client applications, network setups, and query architecture may lessen the effect of these delays and assure more efficient database operations.
FAQs
Q: What is ASYNC_NETWORK_ IO, exactly?
Ans: The SQL Server wait type known as ASYNC_NETWORK_ IO appears when a session awaits a client application to read query results.
Q: Why do ASYNC_NETWORK_ IO delays occur?
Ans: Large result sets, slow client apps, and excessive network latency are frequent culprits.
Q: Which performance effects does ASYNC_NETWORK_ IO have?
Ans: The execution of queries may be delayed, and database performance may suffer.
Q: Can ASYNC_NETWORK_ IO be completely removed?
Ans: It can be reduced but not entirely eliminated in situations with sluggish clients or excessive network latency.
Q: What are the advantages of ASYNC_NETWORK_ IO?
Ans: The answer is that it makes concurrent and non-blocking query execution possible, increasing database throughput.
Q: How may client application performance be improved to lower ASYNC_NETWORK_ IO wait times?
Ans: Implement pagination and optimize code to quickly consume query results.
Q: What network enhancements can lower ASYNC_NETWORK_ IO delay times?
Ans: Reduce network latency by altering network settings and improving infrastructure.
Q: Do SQL Server options exist to reduce ASYNC_NETWORK_ IO?
Ans: While optimizing the server may not completely remove delays, SQL Server settings may assist.
Q: Is the only wait type that affects query performance ASYNC_NETWORK_ IO?
Ans: No, SQL Server contains several wait kinds, each with its causes and fixes.
Q: Is it possible to track ASYNC_NETWORK_ IO waits?
Ans: Yes, tools and DMVs (Dynamic Management Views) are available in SQL Server to track delay data.
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