Performance Tuning with SQL Server Dynamic Management Views

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Chapter 4: Transactions
some point (SQL 11 perhaps) Microsoft makes it easier to parse the information, or normalizes
the information by adding columns to sys.dm_os_waiting_tasks.
The value of the script really becomes evident when one encounters a multi-session
blocking situation. Figure 4.5 shows how it can reveal a real-life blocking chain (one I
encountered just today on one of my servers). I've omitted all security and identifier
columns for my environment, but the remaining data is real.
Figure 4.5: A real-life blocking chain.
Session 65 was blocking Session 63 which, in turn, blocked Session 78, which blocked
70, which blocked both 111 and 87. Session 87 blocked Session 89 which, in turn, blocked
about ten other sessions. My DMO script revealed that Session 65 was the root cause of
the blocking, and the command text returned for this session revealed that I could safely
kill that session. Having done so, and by the time I switched query windows in SSMS to
re-execute the DMO query, the results were clean. All blocking had been resolved.