Tag Archives: Technet

Modified DMV’s in SQL Server 2008 R2 and SQL Server 2012

In this post i will discuss about two dynamic management views that has been enhanced with new columns in SQL Server 2008 R2 and SQL Server 2012. The DMV’s are

1) sys.dm_exec_query_stats
2) sys.dm_exec_sessions

Let us begin with [sys.dm_exec_query_stats]
So what does this view reflect. It reflects performance data for stored query plans in SQL Server plan cache. The data is aggregated and is helpful for performance analysis. When a query plan is eliminated from the plan cache, the related row is also removed. In SQL Server 2008 R2 onwards, 3 new columns have been added to this DMV. They are as follows as explained on Technet.

a) last_rows: The number of rows returned by the last execution of the query.
b) min_rows: Minimum number of rows returned by the query since last recompilation of the query and execution of the plan.
c) max_rows: Maximum number of rows returned by the query over the number of times that the plan has been executed since it was last compiled.

The next dmv that was modified with new columns are [sys.dm_exec_sessions]
This view returns a row per authenticated session on SQL Server. It shows information about all the active user connections and internal tasks that are being performed. The new columns that have been added to this view are as follows:

a) Database_id: iD of the current database for each session.
b) authenticating_database_id:
i) When the source of the session is a contained database, then the value is the db id of the authenticating database.
ii) The value will be 1 if it is a server scoped principal i.e a windows or SQL login.
iii) This will be Null if the session is that of an internal task.
c) open_transaction_count: Number of open transactions per session.

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