SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Troubleshooting Blocking


Troubleshooting Blocking

Author
Message
SQLSACT
SQLSACT
SSCrazy
SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)

Group: General Forum Members
Points: 2106 Visits: 2931
Hi All

I am trying to figure out which queries have caused blocking on my system, or which queries have been victims of blocking.

I have the below script. Correct me if I am wrong, the results of this script is not a definitive list of queries that have been blocked. The difference between the elapsed time and the worker time could be because of any wait type, right?

SELECT TOP 10 
[Average Time Blocked] = (total_elapsed_time - total_worker_time) / qs.execution_count
,[Total Time Blocked] = total_elapsed_time - total_worker_time
,[Execution count] = qs.execution_count
,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
,[Parent Query] = qt.text
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
ORDER BY [Average Time Blocked] DESC;



Is there a way by digging into the plan cache to check for queries that have caused blocking?


Thanks
GilaMonster
GilaMonster
SSC Guru
SSC Guru (88K reputation)SSC Guru (88K reputation)SSC Guru (88K reputation)SSC Guru (88K reputation)SSC Guru (88K reputation)SSC Guru (88K reputation)SSC Guru (88K reputation)SSC Guru (88K reputation)

Group: General Forum Members
Points: 88373 Visits: 45282
SQLSACT (6/19/2013)
The difference between the elapsed time and the worker time could be because of any wait type, right?


Correct, and you could miss queries that have waited, because of parallelism

Is there a way by digging into the plan cache to check for queries that have caused blocking?


No. What's in the plan cache are the plans that the optimiser created for the query and the optimiser doesn't plan for queries to wait or be blocked.

Poll sys.dm_exec_requests, poll sys.dm_os_waiting_tasks, use the blocked process report, set up extended events.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


Fraggle-805517
Fraggle-805517
Ten Centuries
Ten Centuries (1.1K reputation)Ten Centuries (1.1K reputation)Ten Centuries (1.1K reputation)Ten Centuries (1.1K reputation)Ten Centuries (1.1K reputation)Ten Centuries (1.1K reputation)Ten Centuries (1.1K reputation)Ten Centuries (1.1K reputation)

Group: General Forum Members
Points: 1087 Visits: 1512
If you are still using 2005 and don't have Xevents, you could also use profiler. Brad McGehee has an excellent article here:

https://www.simple-talk.com/sql/sql-tools/how-to-identify-blocking-problems-with-sql-profiler/

Fraggle
SQLSACT
SQLSACT
SSCrazy
SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)SSCrazy (2.1K reputation)

Group: General Forum Members
Points: 2106 Visits: 2931
Thanks all
Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search