Returns a row for every worker in the system. For more information about workers, see the Thread and Task Architecture Guide.
To call this from Azure Synapse Analytics (SQL Data Warehouse) or Parallel Data Warehouse, use the name sys.dm_pdw_nodes_os_workers.
|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 (Transact-SQL).|
|context_switch_count||int||Number of scheduler context switches that are performed by this worker.|
|pending_io_count||int||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||bigint||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||bigint||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||Error number of the last exception that this worker encountered.|
|exception_severity||int||Severity of the last exception that this worker encountered.|
|exception_address||varbinary(8)||Code address that threw the exception|
|affinity||bigint||The thread affinity of the worker. Matches the affinity of the thread in sys.dm_os_threads (Transact-SQL).|
|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 milliseconds, at the start of the current run of this worker.|
|end_quantum||bigint||Time, in milliseconds, 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 (Transact-SQL).|
|return_code||int||Return value from last wait. Can be one of the following values:
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 (Transact-SQL).|
|memory_object_address||varbinary(8)||Memory address of the worker memory object. For more information, see sys.dm_os_memory_objects (Transact-SQL).|
|thread_address||varbinary(8)||Memory address of the thread associated with this worker. For more information, see sys.dm_os_threads (Transact-SQL).|
|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 (Transact-SQL).|
|processor_group||smallint||Stores the processor group ID that is assigned to this thread.|
|pdw_node_id||int||Applies to: Azure Synapse Analytics (SQL Data Warehouse), Parallel Data Warehouse
The identifier for the node that this distribution is on.
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.
On SQL Server, requires
VIEW SERVER STATE permission.
On SQL Database Premium Tiers, requires the
VIEW DATABASE STATE permission in the database. On SQL Database Standard and Basic Tiers, requires the
Server Admin role membership, or an
Azure Active Directory admin account.
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_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