Understanding how SQL Server is performing at a macro level is crucial for identifying and resolving performance issues. One way to capture this information is by using Performance Monitor, either on an ad-hoc basis or by setting up a log to capture values on a predefined basis. However, in newer versions of SQL Server, the traditional method of capturing performance monitor counters using the dbo.sysperfinfo table is no longer available.
So, how can we capture Performance Monitor values on an as-needed basis for SQL Server? The solution lies in one of the dynamic management objects called sys.dm_os_performance_counters. This DMV allows us to query a view directly to capture SQL Server counters related to the instance, providing DBAs with the flexibility to capture real-time metrics as issues occur.
Using sys.dm_os_performance_counters is as simple as executing a SELECT statement to retrieve the SQL Server performance metrics. The result set of this query will consist of five columns and over 500 counters, which may vary depending on the applications and services installed on the SQL Server instance.
Column Explanation:
- object_name: Counter category, such as MSSQL + $ + InstanceName: + Databases (if you have an instance)
- counter_name: Counter name relative to the category
- instance_name: Instance of the counter, either a database value or NULL for overall SQL Server
- cntr_value: The captured or calculated value for the counter
- cntr_type: Counter type defined by Performance Monitor
The counters available through sys.dm_os_performance_counters cover a wide range of metrics, including memory usage, SQL Server application-specific counters, and more. Some examples of these counters include MSSQL:CLR, MSSQL:Access Methods, MSSQL:User Settable, MSSQL:Buffer Manager, and MSSQL:Wait Statistics.
It’s important to note that sys.dm_os_performance_counters is limited to SQL Server counters only. If you need to capture system, physical disk, network interface card, or other counters, you will still need to use Performance Monitor.
By leveraging sys.dm_os_performance_counters, DBAs can easily capture and analyze SQL Server performance metrics in real-time, allowing for quicker identification and resolution of performance issues. This powerful tool provides valuable insights into how SQL Server is utilizing resources and helps optimize its overall performance.