Understanding Status In DMVs

Ewald Cress looks at a number of DMVs and how they expose query status:

sys.dm_exec_sessions: status

This metric is completely disjunct from the above ones, and mostly reflects attributes of a CSession class instance. The respective values are derived through the following decision tree:

  • If the internal Boolean member m_fIsConnReset is set, return dormant

  • Else if a flag living outside of CSession itself is set, return preconnect (I’ll touch on the source of this mystery flag below)

  • Else if a flag within the CSession itself is set (indicating that it has been provided some work to do) return running

  • Else return sleeping

It’s interesting to see how something so very similar can have so many different understandings.

Related Posts

SQL Server’s Referential Integrity Operator

Joe Obbish explains the purpose of the referential integrity operator in SQL Server 2016: What would happen if a parent table was referenced by hundreds of child tables, such as for a date dimension table? Deleting or updating a row in the parent table would create a query plan with at least one join per […]

Read More

How Non-Clustered Index Key Columns Are Stored

Kendra Little walks through page-level details on a non-clustered index: Just like in the root page and the intermediate pages, the FirstName and RowID columns are present. Also in the leaf: CharCol, our included column appears! It was not in any of the other levels we inspected, because included columns only exist in the leaf of a […]

Read More

Categories

November 2016
MTWTFSS
« Oct Dec »
 123456
78910111213
14151617181920
21222324252627
282930