Building diagnostic queries using DMVs and DMFs
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The document introduces Diagnostic Management Views (DMVs) and Dynamic Management Functions (DMFs) in SQL Server. It discusses that DMVs and DMFs return server state information and can be used to monitor server health, diagnose problems, and tune performance. It provides examples of common DMVs and DMFs used for query execution and the query plan cache. Finally, it notes that the presentation will demonstrate troubleshooting with DMVs and DMFs.
Building diagnostic queries using DMVs and DMFs
- 2. Building Diagnostic Queries Using DMVs and DMFs Greek MVPs in Action Virtual Event Mar 29, 2020
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- 9. Presentation Content Building Diagnostic Queries Using DMVs and DMFs • What is DMVs/DMFs • Query Execution DMVs/DMFs • Query Plan cache DMVs/DMFs • Troubleshooting with DMVs/DMFs
- 10. • DMVs and DMFs return server-state information - They are virtual objects that return state information - The state is cleared when the server instance is restarted or an administrator clears the state information. • Can be used - monitor the health of a server instance - diagnose problems - tune performance • Two types: - Server-scoped—require VIEW SERVER STATE permission - Database-scoped—require VIEW DATABASE STATE permission • All DMVs and DMFs exist in the sys schema and follow the naming convention dm_%. - They are defined in the resource database and are mapped to other databases. What is DMVs/DMFs Introduced as a new concept in SQL Server 2005
- 11. • sys.dm_exec_sessions (DMV) - Returns one row per authenticated session on SQL Server, shows information about all active user connections and internal tasks • sys.dm_exec_requests (DMV) - Returns information about each request that is executing in SQL Server • sys.dm_exec_sql_text (DMF) - Returns the text of the SQL batch that is identified by the specified sql_handle • sys.dm_exec_input_buffer (DMF) - Returns information about statements submitted to an instance of SQL Server. • sys.dm_os_waiting_tasks (DMV) - Returns information about the wait queue of tasks that are waiting on some resource. Query Execution DMVs/DMFs The most common Query Execution DMVs/DMFs in usage
- 12. • sys.dm_exec_query_stats (DMV) - Returns aggregate performance statistics for cached query plans in SQL Server. • sys.dm_exec_query_plan (DMF) - Returns the Showplan in XML format for the batch specified by the plan handle. The plan specified by the plan handle can either be cached or currently executing. • sys.dm_exec_cached_plans (DMV) - Returns a row for each query plan that is cached by SQL Server for faster query execution. • sys.dm_exec_procedure_stats (DMV) - Returns aggregate performance statistics for cached stored procedures. • sys.dm_exec_function_stats (DMV) - Returns aggregate performance statistics for cached functions. • sys.dm_exec_trigger_stats - Returns aggregate performance statistics for cached triggers. Query Plan cache DMVs/DMFs Provide information about queries that are currently in the plan cache
- 14. Any questions
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