Building diagnostic queries using DMVs and DMFs Greek MVPs in Action Virtual Event Mar 29, 2020

2. Building Diagnostic Queries
Using DMVs and DMFs
Greek MVPs in Action
Virtual Event
Mar 29, 2020

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5. Antonios Chatzipavlis
Data Solutions Consultant & Trainer
Since 1999
30+Years in a Field
20+
Experience with
60+
Certifications
SQLschool.gr
Founder

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10
Celebrating
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years

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

13. Demonstration
Troubleshooting with DMVs/DMFs

14. Any
questions

15. Thank you!
@antoniosch - @sqlschool
./sqlschoolgr - ./groups/sqlschool
./c/SqlschoolGr
SQLschool.gr Group
Antonios Chatzipavlis
Data Solutions Consultant & Trainer

16. A community for Greek professionals who use the Microsoft Data Platform
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