Activity monitor, Script to find Head blocker- SQL Server 2005, 2008 and later

This is very handy useful script in production environment. Even the activity monitor does  the same but when there is high server high activity then your activity monitor hangs and do not respond. Also it is not recommended to use activity monitor for long in production environments as it uses high resources.

SELECT
   [Session ID]    = s.session_id,
   [User Process]  = CONVERT(CHAR(1), s.is_user_process),
   [Login]         = s.login_name,  
   [Database]      = ISNULL(db_name(p.dbid), N''),
   [Task State]    = ISNULL(t.task_state, N''),
   [Command]       = ISNULL(r.command, N''),
   [Application]   = ISNULL(s.program_name, N''),
   [Wait Time (ms)]     = ISNULL(w.wait_duration_ms, 0),
   [Wait Type]     = ISNULL(w.wait_type, N''),
   [Wait Resource] = ISNULL(w.resource_description, N''),
   [Blocked By]    = ISNULL(CONVERT (varchar, w.blocking_session_id), ''),
   [Head Blocker]  =
        CASE
            -- session has an active request, is blocked, but is blocking others or session is idle but has an open tran and is blocking others
            WHEN r2.session_id IS NOT NULL AND (r.blocking_session_id = 0 OR r.session_id IS NULL) THEN '1'
            -- session is either not blocking someone, or is blocking someone but is blocked by another party
            ELSE ''
        END,
   [Total CPU (ms)] = s.cpu_time,
   [Total Physical I/O (MB)]   = (s.reads + s.writes) * 8 / 1024,
   [Memory Use (KB)]  = s.memory_usage * 8192 / 1024,
   [Open Transactions] = ISNULL(r.open_transaction_count,0),
   [Login Time]    = s.login_time,
   [Last Request Start Time] = s.last_request_start_time,
   [Host Name]     = ISNULL(s.host_name, N''),
   [Net Address]   = ISNULL(c.client_net_address, N''),
   [Execution Context ID] = ISNULL(t.exec_context_id, 0),
   [Request ID] = ISNULL(r.request_id, 0),
   [Workload Group] = ISNULL(g.name, N'')
FROM sys.dm_exec_sessions s LEFT OUTER JOIN sys.dm_exec_connections c ON (s.session_id = c.session_id)
LEFT OUTER JOIN sys.dm_exec_requests r ON (s.session_id = r.session_id)
LEFT OUTER JOIN sys.dm_os_tasks t ON (r.session_id = t.session_id AND r.request_id = t.request_id)
LEFT OUTER JOIN
(
    -- In some cases (e.g. parallel queries, also waiting for a worker), one thread can be flagged as
    -- waiting for several different threads.  This will cause that thread to show up in multiple rows
    -- in our grid, which we don't want.  Use ROW_NUMBER to select the longest wait for each thread,
    -- and use it as representative of the other wait relationships this thread is involved in.
    SELECT *, ROW_NUMBER() OVER (PARTITION BY waiting_task_address ORDER BY wait_duration_ms DESC) AS row_num
    FROM sys.dm_os_waiting_tasks
) w ON (t.task_address = w.waiting_task_address) AND w.row_num = 1
LEFT OUTER JOIN sys.dm_exec_requests r2 ON (s.session_id = r2.blocking_session_id)
LEFT OUTER JOIN sys.dm_resource_governor_workload_groups g ON (g.group_id = s.group_id)--TAKE THIS dmv OUT TO WORK IN 2005
LEFT OUTER JOIN sys.sysprocesses p ON (s.session_id = p.spid)
ORDER BY s.session_id;