How to: Identify Blocked SQL Processes Quickly

There was a great article in Visual Studio magazine (June 2008) by Ian Stirk in which he talks in detail about how to improve application performance by creating a utility that tells you which processes are being blocked.

You can read the article at The two sql sprocs that you will need to create are:

The database utility dba_BlockTracer extracts data about the running processes by inspecting the system view sys.sysprocesses. This view then queries the underlying system table sysprocesses.

CREATE PROC [dbo].[dba_BlockTracer]




Purpose: Shows details of the root blocking process, together with details of any blocked processed


Parameters: None.

Revision History:

      19/07/2007 Initial version

Example Usage:

   1. exec YourServerName.master.dbo.dba_BlockTracer



   -- Do not lock anything, and do not get held up by any locks.



   -- If there are blocked processes...

   IF EXISTS(SELECT 1 FROM sys.sysprocesses WHERE

      blocked != 0)


      -- Identify the root-blocking spid(s)

      SELECT distinct t1.spid AS [Root blocking spids]

         , t1.[loginame] AS [Owner]

         , master.dbo.dba_GetSQLForSpid(t1.spid) AS

            'SQL Text'

         , t1.[cpu]

         , t1.[physical_io]

         , DatabaseName = DB_NAME(t1.[dbid])

         , t1.[program_name]

         , t1.[hostname]

         , t1.[status]

         , t1.[cmd]

         , t1.[blocked]

         , t1.[ecid]

      FROM sys.sysprocesses t1, sys.sysprocesses t2

      WHERE t1.spid = t2.blocked

        AND t1.ecid = t2.ecid

        AND t1.blocked = 0

      ORDER BY t1.spid, t1.ecid

      -- Identify the spids being blocked.

      SELECT t2.spid AS 'Blocked spid'

         , t2.blocked AS 'Blocked By'

         , t2.[loginame] AS [Owner]

         , master.dbo.dba_GetSQLForSpid(t2.spid) AS

            'SQL Text'

         , t2.[cpu]

         , t2.[physical_io]

         , DatabaseName = DB_NAME(t2.[dbid])

         , t2.[program_name]

         , t2.[hostname]

         , t2.[status]

         , t2.[cmd]

         , t2.ecid

      FROM sys.sysprocesses t1, sys.sysprocesses t2

      WHERE t1.spid = t2.blocked

        AND t1.ecid = t2.ecid

      ORDER BY t2.blocked, t2.spid, t2.ecid


   ELSE -- No blocked processes.

      PRINT 'No processes blocked.'


Make a call to the database function dba_GetSQLForSpid to get the underlying SQL, which can show you why performance is slow. The function accepts one parameter: the SQL Server process ID (@spid) of a running process.

CREATE Function [dbo].[dba_GetSQLForSpid]


   @spid SMALLINT




Purpose: Returns the SQL text for a given spid.


Parameters: @spid - SQL Server process ID.

Returns: @SqlText - SQL text for a given spid.

Revision History:

      01/12/2006 Initial version

Example Usage:

   SELECT dbo.dba_GetSQLForSpid(51)

   SELECT dbo.dba_GetSQLForSpid(spid) AS [SQL text]

      , * FROM sys.sysprocesses WITH (NOLOCK)



   DECLARE @SqlHandle BINARY(20)

   DECLARE @SqlText NVARCHAR(4000)

   -- Get sql_handle for the given spid.

   SELECT @SqlHandle = sql_handle

      FROM sys.sysprocesses WITH (nolock) WHERE

      spid = @spid

   -- Get the SQL text for the given sql_handle.

   SELECT @SqlText = [text] FROM


   RETURN @SqlText