In this article, you will play around with some SQL Script to identify blocking behaviour. The most basic script that I have been using and used by many DBA will include Activity Monitor, sp_who2, sysprocesses etc.
Recently, I saw a script written by one person:
SELECT * FROM sys.dm_os_waiting_tasks
WHERE blocking_session_id IS NOT NULL
GO
This will shows the rows like:
This is so cool because I know who is waiting for whom. In the above image 53 is waiting for 68. While 79 is waiting for 53. This was a cool way to look at things. Sure, you wanted to show the same data in slightly different way using T-SQL. So, I wrote a Blocking Tree TSQL script:
SET NOCOUNT ON
GO
SELECT SPID, BLOCKED, REPLACE (REPLACE (T.TEXT, CHAR(10), ' '), CHAR (13), ' ' ) AS BATCH
INTO #T
FROM sys.sysprocesses R CROSS APPLY sys.dm_exec_sql_text(R.SQL_HANDLE) T
GO
WITH BLOCKERS (SPID, BLOCKED, LEVEL, BATCH)
AS
(
SELECT SPID,
BLOCKED,
CAST (REPLICATE ('0', 4-LEN (CAST (SPID AS VARCHAR))) + CAST (SPID AS VARCHAR) AS VARCHAR (1000)) AS LEVEL,
BATCH FROM #T R
WHERE (BLOCKED = 0 OR BLOCKED = SPID)
AND EXISTS (SELECT * FROM #T R2 WHERE R2.BLOCKED = R.SPID AND R2.BLOCKED <> R2.SPID)
UNION ALL
SELECT R.SPID,
R.BLOCKED,
CAST (BLOCKERS.LEVEL + RIGHT (CAST ((1000 + R.SPID) AS VARCHAR (100)), 4) AS VARCHAR (1000)) AS LEVEL,
R.BATCH FROM #T AS R
INNER JOIN BLOCKERS ON R.BLOCKED = BLOCKERS.SPID WHERE R.BLOCKED > 0 AND R.BLOCKED <> R.SPID
)
SELECT N' ' + REPLICATE (N'| ', LEN (LEVEL)/4 - 1) +
CASE WHEN (LEN(LEVEL)/4 - 1) = 0
THEN 'HEAD - '
ELSE '|------ ' END
+ CAST (SPID AS NVARCHAR (10)) + N' ' + BATCH AS BLOCKING_TREE
FROM BLOCKERS ORDER BY LEVEL ASC
GO
DROP TABLE #T
GO
The output would look like:
That's a simple way to look at the same Blocking data inside SSMS.
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