Performance Impact of Slow Running Queries In SQL Server

Puran Kandpal | Modified: January 31st, 2019 | SQL |

Introduction:

There could be several reasons behind SQL Server bad performance. One such major reason reported is the slowness of SQL Server and its different segments. Slow running queries in SQL server can be caused by bad physical structure of a database or may be due to the latency in network communication etc. Another problem with long running queries is the issue in configuration of SQL Server. The following section focus on describing why is SQL query running slow in SQL Server and what are the troubleshooting tips to overcome SQL performance issues.

Why SQL Query Running Slow in SQL Server?

Without knowing the root cause of slow running queries in SQL Server, It is tough for a DBA to troubleshoot the problem. Therefore, it is important to check efficiency of all the components before going to use any query optimizer or any other mechanism. This efficient check will help to understand whether the root cause of the problem is related to the component or by queries. Before setting the hand to task, go through the following tips:

  • If the problem is related to latency of the network, then it is important for a DBA to check for other components too, if they are also contributing for the slow running queries.
  • Another reason behind SQL performance issue could be a bad index creation or accessing a bad index from the specified queries.
  • Choosing a slow execution plan may degrade the performance.
  • Running a single query at a time may happen smooth, but running multiple queries at the same time may degrades Server performance.
  • A poorly written code can also be the reason of poor performance of SQL server.

There can be many reasons behind slow running queries in SQL Server that can impact the performance of a SQL Server and may cause the latency of a process. Next, let us understand how to identify the exact issues behind the trouble.

How to Identify Slow Running Queries In SQL Server?

  • If someone is experiencing a bad performance issue with SQL Server components, then adapting the Windows System Monitor might be helpful. With Windows System Monitor, performance of SQL Server and Non-SQL Server components can be monitored.
  • Using SQL Server Profiler will help in improving the performance issues that are related to queries. This method is also helpful to identify slow running queries In SQL Server.
  • There are some dynamic management views (DMVs) sys.dm_exec_query_stats and sys.dm_exec_requests available to check long running queries (Queries that holds a large number of resources) in SQL Server.

After selecting second and third method from above mentioned options, one can identify the queries executed by the SQL Server query optimizer. And one can also determine the indexes that are being used and thus make the changes to improve the performance by modifying the query, Indexes and database design.

The SQL Server query optimizer takes help from statistics to build query plans which could be helpful in improving the query performance. In general, it builds a good stats for some good query plan. In addition, one can also modify or update a query plan by using UPDATE STATISTIC statement or by using the sp_updatestats for the best results.

Conclusion:

While working with SQL Server, user can experience some slow running queries in SQL server, which may be encountered as a bad performance of SQL Server. Once any such problems are reported the main aim should be to identify the root cause of this performance related problems. To identify and fix those troubling issue in SQL server the above mentioned tips will be highly useful. SQL Server provides few helpful options like SQL Server Management Studio, SQL Server Profiler and Transact-SQL SET options that displays query execution plans, one can use these tools also to improve the performance of SQL Server.