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Dynamic Management Views or DMVs are valuable assets for SQL Server professionals who routinely manage SQL instances. Using DMVs, we can retrieve real-time server state information to provide insights into performance, identify potential issues, and determine possible solutions.
What are Dynamic Management Views (DMVs)?
DMVs were introduced in SQL Server 2005 to allow administrators to monitor the health of the server through server state information. They provide unique insights about what is happening within your SQL Server instances. You can interrogate these views using standard SQL commands rather than using performance counters, profiler traces, etc. DMVs are grouped into two main types: server-scoped DMVs and Database-scoped DMVs.
Using DMVs
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--Check the status of all sessions that are active in the server SELECT * FROM sys.dm_exec_sessions |
This DMV, sys.dm_exec_sessions, provides session-level information, such as login time, last request start time, database id, CPU time, memory usage, etc. It’s essential for analyzing the performance impact of individual sessions and identifying problematic or resource-intensive sessions.
Example of a server scoped DMV
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--Display the cached plans in the plan cache SELECT * FROM sys.dm_exec_cached_plans |
This DMV, sys.dm_exec_cached_plans, allows you to see the cached query plans. This can be beneficial if you want to monitor your SQL Server’s overall health as it can help identify costly queries impacting the plan cache and thus server performance.
Example of a Database scoped DMV
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--Get a report of missing indexes SELECT * FROM sys.dm_db_missing_index_details |
The DMV, sys.dm_db_missing_index_details, provides information about missing indexes, which can significantly affect database performance. With this information, DBAs can create necessary indexes and improve overall database performance.
Conclusion:
DMVs are a powerful tool in understanding what’s happening within SQL Server. With various views at both server and individual database levels, they provide extensive visibility into performance, usage and potential bottlenecks, empowering DBAs in their quest for reliably high-performing servers.