How to find out what is locking my tables?

Question

I have a SQL table that all of a sudden cannot return data unless I include with (nolock) on the end, which indicates some kind of lock left on my table.

I've experimented a bit with sys.dm_tran_locks to identify that there are in fact a number of locks on the table, but how do I identify what is locking them (ie the request element of the sys.dm_tran_locks)?

EDIT: I know about sp_lock for pre SQL 2005, but now that that sp is deprecated, AFAIK the right way to do this is with sys.dm_tran_locks. I'm using SQL Server 2008 R2.

Solution 1

Take a look at the following system stored procedures, which you can run in SQLServer Management Studio (SSMS):

• sp_who
• sp_lock

Also, in SSMS, you can view locks and processes in different ways:

Different versions of SSMS put the activity monitor in different places. For example, SSMS 2008 and 2012 have it in the context menu when you right-click on a server node.

Solution 2

For getting straight to "who is blocked/blocking" I combined/abbreviated sp_who and sp_lock into a single query which gives a nice overview of who has what object locked to what level.

--Create Procedure WhoLock
--AS
set nocount on
if object_id('tempdb..#locksummary') is not null Drop table #locksummary
if object_id('tempdb..#lock') is not null Drop table #lock
create table #lock (    spid int,    dbid int,    objId int,    indId int,    Type char(4),    resource nchar(32),    Mode char(8),    status char(6))
Insert into #lock exec sp_lock
if object_id('tempdb..#who') is not null Drop table #who
create table #who (     spid int, ecid int, status char(30),
            loginame char(128), hostname char(128),
            blk char(5), dbname char(128), cmd char(16)
            --
            , request_id INT --Needed for SQL 2008 onwards
            --
         )
Insert into #who exec sp_who
Print '-----------------------------------------'
Print 'Lock Summary for ' + @@servername  + ' (excluding tempdb):'
Print '-----------------------------------------' + Char(10)
Select     left(loginame, 28) as loginame, 
    left(db_name(dbid),128) as DB,
    left(object_name(objID),30) as object,
    max(mode) as [ToLevel],
    Count(*) as [How Many],
    Max(Case When mode= 'X' Then cmd Else null End) as [Xclusive lock for command],
    l.spid, hostname
into #LockSummary
from #lock l join #who w on l.spid= w.spid
where dbID != db_id('tempdb') and l.status='GRANT'
group by dbID, objID, l.spid, hostname, loginame

Select * from #LockSummary order by [ToLevel] Desc, [How Many] Desc, loginame, DB, object

Print '--------'
Print 'Who is blocking:'
Print '--------' + char(10)
SELECT p.spid
,convert(char(12), d.name) db_name
, program_name
, p.loginame
, convert(char(12), hostname) hostname
, cmd
, p.status
, p.blocked
, login_time
, last_batch
, p.spid
FROM      master..sysprocesses p
JOIN      master..sysdatabases d ON p.dbid =  d.dbid
WHERE     EXISTS (  SELECT 1
          FROM      master..sysprocesses p2
          WHERE     p2.blocked = p.spid )

Print '--------'
Print 'Details:'
Print '--------' + char(10)
Select     left(loginame, 30) as loginame,  l.spid,
    left(db_name(dbid),15) as DB,
    left(object_name(objID),40) as object,
    mode ,
    blk,
    l.status
from #lock l join #who w on l.spid= w.spid
where dbID != db_id('tempdb') and blk <>0
Order by mode desc, blk, loginame, dbID, objID, l.status

(For what the lock level abbreviations mean, see e.g. https://technet.microsoft.com/en-us/library/ms175519%28v=sql.105%29.aspx)

Copied from: sp_WhoLock – a T-SQL stored proc combining sp_who and sp_lock...

NB the [Xclusive lock for command] column can be misleading -- it shows the current command for that spid; but the X lock could have been triggered by an earlier command in the transaction.

Solution 3

exec sp_lock

This query should give you existing locks.

exec sp_who SPID -- will give you some info

Having spids, you could check activity monitor(processes tab) to find out what processes are locking the tables ("details" for more info and "kill process" to kill it).

Solution 4

I have a stored procedure that I have put together, that deals not only with locks and blocking, but also to see what is running in a server. I have put it in master. I will share it with you, the code is below:

USE [master]
go


CREATE PROCEDURE [dbo].[sp_radhe] 

AS
BEGIN

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED


-- the current_processes
-- marcelo miorelli 
-- CCHQ 
-- 04 MAR 2013 Wednesday

SELECT es.session_id AS session_id
,COALESCE(es.original_login_name, '') AS login_name
,COALESCE(es.host_name,'') AS hostname
,COALESCE(es.last_request_end_time,es.last_request_start_time) AS last_batch
,es.status
,COALESCE(er.blocking_session_id,0) AS blocked_by
,COALESCE(er.wait_type,'MISCELLANEOUS') AS waittype
,COALESCE(er.wait_time,0) AS waittime
,COALESCE(er.last_wait_type,'MISCELLANEOUS') AS lastwaittype
,COALESCE(er.wait_resource,'') AS waitresource
,coalesce(db_name(er.database_id),'No Info') as dbid
,COALESCE(er.command,'AWAITING COMMAND') AS cmd
,sql_text=st.text
,transaction_isolation =
CASE es.transaction_isolation_level
    WHEN 0 THEN 'Unspecified'
    WHEN 1 THEN 'Read Uncommitted'
    WHEN 2 THEN 'Read Committed'
    WHEN 3 THEN 'Repeatable'
    WHEN 4 THEN 'Serializable'
    WHEN 5 THEN 'Snapshot'
END
,COALESCE(es.cpu_time,0) 
    + COALESCE(er.cpu_time,0) AS cpu
,COALESCE(es.reads,0) 
    + COALESCE(es.writes,0) 
    + COALESCE(er.reads,0) 
+ COALESCE(er.writes,0) AS physical_io
,COALESCE(er.open_transaction_count,-1) AS open_tran
,COALESCE(es.program_name,'') AS program_name
,es.login_time
FROM sys.dm_exec_sessions es
LEFT OUTER JOIN sys.dm_exec_connections ec ON es.session_id = ec.session_id
LEFT OUTER JOIN sys.dm_exec_requests er ON es.session_id = er.session_id
LEFT OUTER JOIN sys.server_principals sp ON es.security_id = sp.sid
LEFT OUTER JOIN sys.dm_os_tasks ota ON es.session_id = ota.session_id
LEFT OUTER JOIN sys.dm_os_threads oth ON ota.worker_address = oth.worker_address
CROSS APPLY sys.dm_exec_sql_text(er.sql_handle) AS st
where es.is_user_process = 1 
  and es.session_id <> @@spid
  and es.status = 'running'
ORDER BY es.session_id

end 

GO

this procedure has done very good for me in the last couple of years. to run it just type sp_radhe

Regarding putting sp_radhe in the master database

I use the following code and make it a system stored procedure

exec sys.sp_MS_marksystemobject 'sp_radhe'

as you can see on the link below

Creating Your Own SQL Server System Stored Procedures

Regarding the transaction isolation level

Questions About T-SQL Transaction Isolation Levels You Were Too Shy to Ask

Jonathan Kehayias

Once you change the transaction isolation level it only changes when the scope exits at the end of the procedure or a return call, or if you change it explicitly again using SET TRANSACTION ISOLATION LEVEL.

In addition the TRANSACTION ISOLATION LEVEL is only scoped to the stored procedure, so you can have multiple nested stored procedures that execute at their own specific isolation levels.

Solution 5

This should give you all the details of the existing locks.

DECLARE @tblVariable TABLE(SPID INT, Status VARCHAR(200), [Login] VARCHAR(200), HostName VARCHAR(200), 
    BlkBy VARCHAR(200), DBName VARCHAR(200), Command VARCHAR(200), CPUTime INT, 
    DiskIO INT, LastBatch VARCHAR(200), ProgramName VARCHAR(200), _SPID INT, 
    RequestID INT)

INSERT INTO @tblVariable
EXEC Master.dbo.sp_who2

SELECT v.*, t.TEXT 
FROM @tblVariable v
INNER JOIN sys.sysprocesses sp ON sp.spid = v.SPID
CROSS APPLY sys.dm_exec_sql_text(sp.sql_handle) AS t
ORDER BY BlkBy DESC, CPUTime DESC

You can then kill, with caution, the SPID that blocks your table.

kill 104 -- Your SPID

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