Click here to Skip to main content
11,704,509 members (56,567 online)
Click here to Skip to main content

List blocking processes in SQL server

, 11 Oct 2011 CPOL 24.8K 8
Rate this:
Please Sign up or sign in to vote.
A quick script to enable you to find the processes that are blocking in SQL server
We use this quick script to list those processes that are blocking other processes in SQL server. What you do with the information is up to you, but we suggest checking to ensure you're only locking when you need to (SET READ UNCOMMITTED or use NOLOCK, ROWLOCK hints if appropriate), and we also suggest you review your SQL setup: is your hardware fast enough? Have you separated out your logging, data and tempDB files onto separate volumes?

Usage: ListBlocking [@KillOrphanedProcesses = 0]

If @KillOrphanedProcesses is set to 1 then the script will attempt to kill orphaned processes.

WHERE object_id = OBJECT_ID(N'[dbo].[ListBlocking]') 
AND type in (N'P', N'PC'))
EXEC dbo.sp_executesql @statement = N'CREATE PROCEDURE [dbo].[ListBlocking] AS'
Description:    Wrapper to sp_who2 to show only those processes that 
                are blocking. 
                Please see for
                more info on locking.
ALTER procedure ListBlocking
    @KillOrphanedProcesses bit = 0
IF OBJECT_ID('tempdb..#Process') IS NOT NULL drop table #Process
IF OBJECT_ID('tempdb..#BlockingProcess') IS NOT NULL drop table #BlockingProcess
create table #Process (
    SPID int,
    Status varchar(500),
    Login varchar(500),
    Hostname varchar(500),
    BlkBy varchar(50),
    DBName varchar(500),
    Command varchar(500),
    CPUTime int,
    DiskIO int,
    LastBatch varchar(500),
    ProgramName varchar(500),
    SPID2 int,
    RequestId int
CREATE TABLE #BlockingProcess (
    BlockingProcessID int IDENTITY(1,1),
    ProcessID varchar(20),
    EventType varchar(100),
    Parameters varchar(100),
    EventInfo varchar(500),
    CPUTime int,
    DiskIO int,
    TransactionCount int
DECLARE @BlockingPID        varchar(20),
        @CPUTime            int, 
        @DiskIO             int,
        @TransactionCount   int
-- Let SQL Server get us a list of what's going on
insert into #Process exec sp_who2
-- From this list of what's going on, get those items that are blocked, and loop through them
    SELECT BlkBy, SUM(CPUTime) as CPUTime, SUM(DiskIO) as DiskIO
    FROM #Process
    WHERE ISNULL(BlkBy,'') <> ''
    GROUP BY BlkBy
OPEN ProcessCursor
FETCH NEXT FROM ProcessCursor INTO @BlockingPID, @CPUTime, @DiskIO
    -- Only valid PIDs
    if ISNULL(@BlockingPID, '') <> '' and @BlockingPID <> '0' AND @BlockingPID <> '  .'
        -- For each blocked process get what information we can on the process and what's blocking it
        SET @TransactionCount = 0
        --  -2 = The blocking resource is owned by an orphaned distributed transaction.
        IF SUBSTRING(@BlockingPID, 1, 2) = '-2' 
            -- For orphaned processes we need to get the Unit of work if we're to do anything with it
            DECLARE @UnitOfWork varchar(50)
            select top 1 @UnitOfWork = ISNULL(req_transactionUOW, '')
            from master..syslockinfo
            where req_spid = -2
            if @KillOrphanedProcesses = 1
                if @UnitOfWork <> '' exec('KILL ''' + @UnitOfWork + '''')
                INSERT INTO #BlockingProcess (EventType, Parameters, EventInfo)
                VALUES('', '', '- Killed UOW ' + @UnitOfWork + ' -')
                INSERT INTO #BlockingProcess (EventType, Parameters, EventInfo)
                VALUES('', '', '- Orphaned. UOW = ' + @UnitOfWork + ' -')
        -- -3 = The blocking resource is owned by a deferred recovery transaction.
        ELSE IF SUBSTRING(@BlockingPID, 1, 2) = '-3' 
            INSERT INTO #BlockingProcess (EventType, Parameters, EventInfo)
            VALUES('', '', '- deferred recovery transaction -')
        -- -4 = Session ID of the blocking latch owner could not be determined at this 
        --      time because of internal latch state transitions.
        ELSE IF SUBSTRING(@BlockingPID, 1, 2) = '-4' 
            INSERT INTO #BlockingProcess (EventType, Parameters, EventInfo)
            VALUES('', '', '- Latch owner could not be determined -')
        -- Nothing unusual here. A process is being blocked by another processes, so let's get the
        -- info on the process that's doing the blocking
            SELECT @TransactionCount = open_tran FROM master.sys.sysprocesses WHERE SPID=@BlockingPID
            INSERT INTO #BlockingProcess (EventType, Parameters, EventInfo)
            EXEC ('DBCC INPUTBUFFER(' + @BlockingPID + ') WITH NO_INFOMSGS')
        -- Add some aggregate info on the blocking processes
        UPDATE #BlockingProcess 
        SET ProcessID        = @BlockingPID,
            CPUTime          = @CPUTime,
            DiskIO           = @DiskIO,
            TransactionCount = @TransactionCount
        WHERE BlockingProcessID = SCOPE_IDENTITY()
    FETCH NEXT FROM ProcessCursor INTO @BlockingPID, @CPUTime, @DiskIO
CLOSE ProcessCursor
DEALLOCATE ProcessCursor
-- Display the results
SELECT ProcessID, EventInfo, TransactionCount, CPUTime, DiskIO FROM #BlockingProcess


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Chris Maunder
Founder CodeProject
Canada Canada
Chris is the Co-founder, Administrator, Architect, Chief Editor and Shameless Hack who wrote and runs The Code Project. He's been programming since 1988 while pretending to be, in various guises, an astrophysicist, mathematician, physicist, hydrologist, geomorphologist, defence intelligence researcher and then, when all that got a bit rough on the nerves, a web developer. He is a Microsoft Visual C++ MVP both globally and for Canada locally.

His programming experience includes C/C++, C#, SQL, MFC, ASP, ASP.NET, and far, far too much FORTRAN. He has worked on PocketPCs, AIX mainframes, Sun workstations, and a CRAY YMP C90 behemoth but finds notebooks take up less desk space.

He dodges, he weaves, and he never gets enough sleep. He is kind to small animals.

Chris was born and bred in Australia but splits his time between Toronto and Melbourne, depending on the weather. For relaxation he is into road cycling, snowboarding, rock climbing, and storm chasing.

You may also be interested in...

Comments and Discussions

GeneralReason for my vote of 5 Brilliant.. Pin
Pravin Patil, Mumbai11-Oct-11 22:32
memberPravin Patil, Mumbai11-Oct-11 22:32 
GeneralReason for my vote of 5 Fine, Thank you. Pin
thatraja11-Oct-11 18:51
mvpthatraja11-Oct-11 18:51 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web03 | 2.8.150819.1 | Last Updated 11 Oct 2011
Article Copyright 2011 by Chris Maunder
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid