Tuning your SQL server is important because it can impact overall server performance. Tuning expensive queries is imperative because your database server’s performance can be affected by a slow and unresponsive query. Monitoring the performance of each query in SQL server is key – for example, if a single query is taking time to respond, you’ll know CPU utilization is high. This causes a strain on other applications using the same SQL. Let’s look at a few reasons that cause a query to perform poorly.
- Server Load: If there’s a sudden spike in your server load then the queries will get slower – this is likely due to other applications like Antivirus scan or backup process running on the server.
- Indexing Issues: If the database isn’t indexed then it’s going to make your queries slower.
- Poorly Written Queries: The time it takes for SQL queries to respond is an indication if the query that’s written needs to be re-written or needs changes in order to improve performance.
- Querying Different Databases: Joining multiple databases and running a query will cause the query to perform poorly because of matching database tables, etc.
Tips to Monitor SQL Server Queries
You can monitor various metrics to determine the most expensive queries and how they affect performance and availability of SQL servers.
- Execution: This metric will show you the number of times the listed query is executed.
- CPU Time: You will know what each query is doing to the CPU load and performance and how much time a listed query took to complete. You can gain insights into whether other applications are being affected when the CPU load is higher than usual.
- Query Duration: You can monitor how long it takes for a query to run. This will really open up and show you real issues that are occurring in the database server when a query is taking longer to respond.
- Logical and Physical Reads: Logical reads will indicate the total number of page access needed to process the query. The physical reads will indicate the number of pages that are read from the disks.
SQL server performance monitoring will tell you the root cause of why issues occur in your database server and gives real insights into expensive queries and why it’s choking your SQL performance. You should be able to see a list of the most expensive queries running across all databases for that SQL server instance.
If you still want to drill-down deeper, you can filter individual queries in a particular database based on time frame, user or host. Using this, you can identify if your colleagues or other users are running a heavy application causing CPU or memory load issues. This allows you to keep a close watch on badly optimized queries from affecting your database performance.
Karthik Ramachandran is a Product Marketing Specialist at SolarWinds who has extensive IT management expertise in systems management including application, server and remote IT management.