sys.dm_os_tasks

Returns one row for each task that is active in the instance of SQL Server.

Column name	Data type	Description
task_address	varbinary(8)	Memory address of the object.
task_state	nvarchar(60)	State of the task. This can be one of the following: PENDING: Waiting for a worker thread. RUNNABLE: Runnable, but waiting to receive a quantum. RUNNING: Currently running on the scheduler. SUSPENDED: Has a worker, but is waiting for an event. DONE: Completed. SPINLOOP: Stuck in a spinlock.
context_switches_count	int	Number of scheduler context switches that this task has completed.
pending_io_count	int	Number of physical I/Os that are performed by this task.
pending_io_byte_count	bigint	Total byte count of I/Os that are performed by this task.
pending_io_byte_average	int	Average byte count of I/Os that are performed by this task.
scheduler_id	int	ID of the parent scheduler. This is a handle to the scheduler information for this task. For more information, see sys.dm_os_schedulers.
session_id	smallint	ID of the session that is associated with the task.
exec_context_id	int	Execution context ID that is associated with the task.
request_id	int	ID of the request of the task. For more information, see sys.dm_exec_requests.
worker_address	varbinary(8)	Memory address of the worker that is running the task. NULL = Task is either waiting for a worker to be able to run, or the task has just finished running. For more information, see sys.dm_os_workers.
host_address	varbinary(8)	Memory address of the host. 0 = Hosting was not used to create the task. This helps identify the host that was used to create this task. For more information, see sys.dm_os_hosts.

Permission

Requires VIEW SERVER STATE permission on the server.

Examples

A. Monitoring parallel requests

For requests that are executed in parallel, you will see multiple rows for the same combination of (<session_id>, <request_id>). Use the following query to find the degree of parallelism for all active requests.

Note

A request_id is unique within a session.

SELECT
    task_address,
    task_state,
    context_switches_count,
    pending_io_count,
    pending_io_byte_count,
    pending_io_byte_average,
    scheduler_id,
    session_id,
    exec_context_id,
    request_id,
    worker_address,
    host_address
  FROM sys.dm_os_tasks
  ORDER BY session_id, request_id;

B. Associating session IDs with Windows threads

You can use the following query to associate a session ID value with a Windows thread ID. You can then monitor the performance of the thread in the Windows Performance Monitor. The following query does not return information for sessions that are sleeping.

SELECT STasks.session_id, SThreads.os_thread_id
  FROM sys.dm_os_tasks AS STasks
  INNER JOIN sys.dm_os_threads AS SThreads
    ON STasks.worker_address = SThreads.worker_address
  WHERE STasks.session_id IS NOT NULL
  ORDER BY STasks.session_id;
GO

See Also

Reference

Dynamic Management Views and Functions
SQL Server Operating System Related Dynamic Management Views

Other Resources

Memory Architecture

Help and Information

Getting SQL Server 2005 Assistance

Change History

Release	History
14 April 2006	New content: Added example B.
5 December 2005	New content: Added an example.