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sys.dm_os_workers

Updated: 14 April 2006

Returns a row for every worker in the system.

Column name Data type Description

worker_address

varbinary(8)

Memory address of the worker.

status

int

Internal use only.

is_preemptive

bit

1 = Worker is running with preemptive scheduling. Any worker that is running external code is run under preemptive scheduling.

is_fiber

bit

1 = Worker is running with lightweight pooling. For more information, see sp_configure (Transact-SQL).

is_sick

bit

1 = Worker is stuck trying to obtain a spin lock. If this bit is set, this might indicate a problem with contention on a frequently accessed object.

is_in_cc_exception

bit

1 = Worker is currently handling a non-SQL Server exception.

is_fatal_exception

bit

Specifies whether this worker received a fatal exception.

is_inside_catch

bit

1 = Worker is currently handling an exception.

is_in_polling_io_completion_routine

bit

1 = Worker is currently running an I/O completion routine for a pending I/O. For more information, see sys.dm_io_pending_io_requests.

context_switch_count

int

The number of scheduler context switches that are performed by this worker.

pending_io_count

int

The number of physical I/Os that are performed by this worker.

pending_io_byte_count

bigint

Total number of bytes for all pending physical I/Os for this worker.

pending_io_byte_average

int

Average number of bytes for physical I/Os for this worker.

wait_started_ms_ticks

int

Point in time, in ms_ticks, when this worker entered the SUSPENDED state. Subtracting this value from ms_ticks in sys.dm_os_sys_info returns the number of milliseconds that the worker has been waiting.

wait_resumed_ms_ticks

int

Point in time, in ms_ticks, when this worker entered the RUNNABLE state. Subtracting this value from ms_ticks in sys.dm_os_sys_info returns the number of milliseconds that the worker has been in the runnable queue.

task_bound_ms_ticks

bigint

Point in time, in ms_ticks, when a task is bound to this worker.

worker_created_ms_ticks

bigint

Point in time, in ms_ticks, when a worker is created.

exception_num

int

The error number of the last exception that this worker encountered.

exception_severity

int

The severity of the last exception that this worker encountered.

exception_address

varbinary(8)

The code address that threw the exception

locale

int

Locale LCID setting for the worker.

affinity

bigint

Affinity setting for the worker. For more information, see sys.dm_os_schedulers.

state

nvarchar(60)

Worker state. Can be one of the following values:

INIT = Worker is currently being initialized.

RUNNING = Worker is currently running either nonpreemptively or preemptively.

RUNNABLE = The worker is ready to run on the scheduler.

SUSPENDED = The worker is currently suspended, waiting for an event to send it a signal.

start_quantum

bigint

Time, in cpu_ticks, at the start of the current run of this worker.

end_quantum

bigint

Time, in cpu_ticks, at the end of the current run of this worker.

last_wait_type

nvarchar(60)

Type of last wait. For a list of wait types, see sys.dm_os_wait_stats.

return_code

int

Return value from last wait. Can be one of the following values:

0 =SUCCESS

3 = DEADLOCK

4 = PREMATURE_WAKEUP

258 = TIMEOUT

quantum_used

bigint

Internal use only.

max_quantum

bigint

Internal use only.

boost_count

int

Internal use only.

tasks_processed_count

int

Number of tasks that this worker processed.

fiber_address

varbinary(8)

Memory address of the fiber with which this worker is associated.

NULL = SQL Server is not configured for lightweight pooling.

task_address

varbinary(8)

Memory address of the current task. For more information, see sys.dm_os_tasks.

memory_object_address

varbinary(8)

Memory address of the worker memory object. For more information, see sys.dm_os_memory_objects.

thread_address

varbinary(8)

Memory address of the thread associated with this worker. For more information, see sys.dm_os_threads.

signal_worker_address

varbinary(8)

Memory address of the worker that last signaled this object. For more information, see sys.dm_os_workers.

scheduler_address

varbinary(8)

Memory address of the scheduler. For more information, see sys.dm_os_schedulers.

If the worker state is RUNNING and the worker is running nonpreemptively, the worker address matches the active_worker_address in sys.dm_os_schedulers.

When a worker that is waiting on an event is signaled, the worker is placed at the head of the runnable queue. SQL Server allows for this to happen one thousand times in a row, after which the worker is placed at the end of the queue. Moving a worker to the end of the queue has some performance implications.

Requires VIEW SERVER STATE permission on the server.

You can use the following query to find out how long a worker has been running in a SUSPENDED or RUNNABLE state.

SELECT 
    t1.session_id,
    CONVERT(varchar(10), t1.status) AS status,
    CONVERT(varchar(15), t1.command) AS command,
    CONVERT(varchar(10), t2.state) AS worker_state,
    w_suspended = 
      CASE t2.wait_started_ms_ticks
        WHEN 0 THEN 0
        ELSE 
          t3.ms_ticks - t2.wait_started_ms_ticks
      END,
    w_runnable = 
      CASE t2.wait_resumed_ms_ticks
        WHEN 0 THEN 0
        ELSE 
          t3.ms_ticks - t2.wait_resumed_ms_ticks
      END
  FROM sys.dm_exec_requests AS t1
  INNER JOIN sys.dm_os_workers AS t2
    ON t2.task_address = t1.task_address
  CROSS JOIN sys.dm_os_sys_info AS t3
  WHERE t1.scheduler_id IS NOT NULL;

Here is the result set.

session_id status     command         worker_state w_suspended w_runnable
---------- ---------- --------------- ------------ ----------- --------------------
4          background LAZY WRITER     SUSPENDED    688         688
6          background LOCK MONITOR    SUSPENDED    4657        4657
19         background BRKR TASK       SUSPENDED    603820344   603820344
14         background BRKR EVENT HNDL SUSPENDED    63583641    63583641
51         running    SELECT          RUNNING      0           0
2          background RESOURCE MONITO RUNNING      0           603825954
3          background LAZY WRITER     SUSPENDED    422         422
7          background SIGNAL HANDLER  SUSPENDED    603820485   603820485
13         background TASK MANAGER    SUSPENDED    603824704   603824704
18         background BRKR TASK       SUSPENDED    603820407   603820407
9          background TRACE QUEUE TAS SUSPENDED    454         454
52         suspended  SELECT          SUSPENDED    35094       35094
1          background RESOURCE MONITO RUNNING      0           603825954

In the output, when w_runnable and w_suspended are equal, this represents the time that the worker is in the SUSPENDED state. Otherwise, w_runnable represents the time that is spent by the worker in the RUNNABLE state. In the output, session 52 is SUSPENDED for 35,094 milliseconds.

Release History

14 April 2006

Changed content:

Modified description for wait_resumed_ms_ticks.

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