sys.dm_exec_requests (Transact-SQL)

Article
03/03/2023
9 minutes to read

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Returns information about each request that is executing in SQL Server. For more information about requests, see the Thread and Task Architecture Guide.

Note

To call this from dedicated SQL pool in Azure Synapse Analytics or Analytics Platform System (PDW), see sys.dm_pdw_exec_requests (Transact-SQL). For serverless SQL pool use sys.dm_exec_requests.

Column name	Data type	Description
session_id	smallint	ID of the session to which this request is related. Isn't nullable.
request_id	int	ID of the request. Unique in the context of the session. Isn't nullable.
start_time	datetime	Timestamp when the request arrived. Isn't nullable.
status	nvarchar(30)	Status of the request. Can be one of the following values: Background Running Runnable Sleeping Suspended Isn't nullable.
command	nvarchar(32)	Identifies the current type of command that is being processed. Common command types include the following values: SELECT INSERT UPDATE DELETE BACKUP LOG BACKUP DATABASE DBCC FOR The text of the request can be retrieved by using sys.dm_exec_sql_text with the corresponding sql_handle for the request. Internal system processes set the command based on the type of task they perform. Tasks can include the following values: LOCK MONITOR CHECKPOINTLAZY WRITER Isn't nullable.
sql_handle	varbinary(64)	Is a token that uniquely identifies the batch or stored procedure that the query is part of. Is nullable.
statement_start_offset	int	Indicates, in bytes, beginning with 0, the starting position of the currently executing statement for the currently executing batch or persisted object. Can be used together with the `sql_handle`, the `statement_end_offset`, and the `sys.dm_exec_sql_text` dynamic management function to retrieve the currently executing statement for the request. Is nullable.
statement_end_offset	int	Indicates, in bytes, starting with 0, the ending position of the currently executing statement for the currently executing batch or persisted object. Can be used together with the `sql_handle`, the `statement_start_offset`, and the `sys.dm_exec_sql_text` dynamic management function to retrieve the currently executing statement for the request. Is nullable.
plan_handle	varbinary(64)	Is a token that uniquely identifies a query execution plan for a batch that is currently executing. Is nullable.
database_id	smallint	ID of the database the request is executing against. Isn't nullable.
user_id	int	ID of the user who submitted the request. Isn't nullable.
connection_id	uniqueidentifier	ID of the connection on which the request arrived. Is nullable.
blocking_session_id	smallint	ID of the session that is blocking the request. If this column is NULL or equal to 0, the request isn't blocked, or the session information of the blocking session isn't available (or can't be identified). For more information, see Understand and resolve SQL Server blocking problems. -2 = The blocking resource is owned by an orphaned distributed transaction. -3 = The blocking resource is owned by a deferred recovery transaction. -4 = Session ID of the blocking latch owner couldn't be determined at this time because of internal latch state transitions. -5 = Session ID of the blocking latch owner couldn't be determined because it isn't tracked for this latch type (for example, for an SH latch). By itself, blocking_session_id -5 doesn't indicate a performance problem. -5 is an indication that the session is waiting on an asynchronous action to complete. Before -5 was introduced, the same session would have shown blocking_session_id 0, even though it was still in a wait state. Depending on workload, observing -5 as blocking_session_id may be a common occurrence.
wait_type	nvarchar(60)	If the request is currently blocked, this column returns the type of wait. Is nullable. For information about types of waits, see sys.dm_os_wait_stats (Transact-SQL).
wait_time	int	If the request is currently blocked, this column returns the duration in milliseconds, of the current wait. Isn't nullable.
last_wait_type	nvarchar(60)	If this request has previously been blocked, this column returns the type of the last wait. Isn't nullable.
wait_resource	nvarchar(256)	If the request is currently blocked, this column returns the resource for which the request is currently waiting. Isn't nullable.
open_transaction_count	int	Number of transactions that are open for this request. Isn't nullable.
open_resultset_count	int	Number of result sets that are open for this request. Isn't nullable.
transaction_id	bigint	ID of the transaction in which this request executes. Isn't nullable.
context_info	varbinary(128)	CONTEXT_INFO value of the session. Is nullable.
percent_complete	real	Percentage of work completed for the following commands: ALTER INDEX REORGANIZE AUTO_SHRINK option with ALTER DATABASE BACKUP DATABASE DBCC CHECKDB DBCC CHECKFILEGROUP DBCC CHECKTABLE DBCC INDEXDEFRAG DBCC SHRINKDATABASE DBCC SHRINKFILE RECOVERY RESTORE DATABASE ROLLBACK TDE ENCRYPTION Isn't nullable.
estimated_completion_time	bigint	Internal only. Isn't nullable.
cpu_time	int	CPU time in milliseconds that is used by the request. Isn't nullable.
total_elapsed_time	int	Total time elapsed in milliseconds since the request arrived. Isn't nullable.
scheduler_id	int	ID of the scheduler that is scheduling this request. Is nullable.
task_address	varbinary(8)	Memory address allocated to the task that is associated with this request. Is nullable.
reads	bigint	Number of reads performed by this request. Isn't nullable.
writes	bigint	Number of writes performed by this request. Isn't nullable.
logical_reads	bigint	Number of logical reads that have been performed by the request. Isn't nullable.
text_size	int	TEXTSIZE setting for this request. Isn't nullable.
language	nvarchar(128)	Language setting for the request. Is nullable.
date_format	nvarchar(3)	DATEFORMAT setting for the request. Is nullable.
date_first	smallint	DATEFIRST setting for the request. Isn't nullable.
quoted_identifier	bit	1 = QUOTED_IDENTIFIER is ON for the request. Otherwise, it's 0. isn't nullable.
arithabort	bit	1 = ARITHABORT setting is ON for the request. Otherwise, it's 0. isn't nullable.
ansi_null_dflt_on	bit	1 = ANSI_NULL_DFLT_ON setting is ON for the request. Otherwise, it's 0. isn't nullable.
ansi_defaults	bit	1 = ANSI_DEFAULTS setting is ON for the request. Otherwise, it's 0. isn't nullable.
ansi_warnings	bit	1 = ANSI_WARNINGS setting is ON for the request. Otherwise, it's 0. Isn't nullable.
ansi_padding	bit	1 = ANSI_PADDING setting is ON for the request. Otherwise, it's 0. isn't nullable.
ansi_nulls	bit	1 = ANSI_NULLS setting is ON for the request. Otherwise, it's 0. isn't nullable.
concat_null_yields_null	bit	1 = CONCAT_NULL_YIELDS_NULL setting is ON for the request. Otherwise, it's 0. isn't nullable.
transaction_isolation_level	smallint	Isolation level with which the transaction for this request is created. isn't nullable. 0 = Unspecified 1 = ReadUncomitted 2 = ReadCommitted 3 = Repeatable 4 = Serializable 5 = Snapshot
lock_timeout	int	Lock time-out period in milliseconds for this request. isn't nullable.
deadlock_priority	int	DEADLOCK_PRIORITY setting for the request. isn't nullable.
row_count	bigint	Number of rows that have been returned to the client by this request. isn't nullable.
prev_error	int	Last error that occurred during the execution of the request. isn't nullable.
nest_level	int	Current nesting level of code that is executing on the request. isn't nullable.
granted_query_memory	int	Number of pages allocated to the execution of a query on the request. isn't nullable.
executing_managed_code	bit	Indicates whether a specific request is currently executing common language runtime objects, such as routines, types, and triggers. it's set for the full time a common language runtime object is on the stack, even while running Transact-SQL from within common language runtime. isn't nullable.
group_id	int	ID of the workload group to which this query belongs. isn't nullable.
query_hash	binary(8)	Binary hash value calculated on the query and used to identify queries with similar logic. You can use the query hash to determine the aggregate resource usage for queries that differ only by literal values.
query_plan_hash	binary(8)	Binary hash value calculated on the query execution plan and used to identify similar query execution plans. You can use query plan hash to find the cumulative cost of queries with similar execution plans.
statement_sql_handle	varbinary(64)	Applies to: SQL Server 2014 (12.x) and later. SQL handle of the individual query. This column is NULL if Query Store isn't enabled for the database.
statement_context_id	bigint	Applies to: SQL Server 2014 (12.x) and later. The optional foreign key to sys.query_context_settings. This column is NULL if Query Store isn't enabled for the database.
dop	int	Applies to: SQL Server 2016 (13.x) and later. The degree of parallelism of the query.
parallel_worker_count	int	Applies to: SQL Server 2016 (13.x) and later. The number of reserved parallel workers if this is a parallel query.
external_script_request_id	uniqueidentifier	Applies to: SQL Server 2016 (13.x) and later. The external script request ID associated with the current request.
is_resumable	bit	Applies to: SQL Server 2017 (14.x) and later. Indicates whether the request is a resumable index operation.
page_resource	binary(8)	Applies to: SQL Server 2019 (15.x) An 8-byte hexadecimal representation of the page resource if the `wait_resource` column contains a page. For more information, see sys.fn_PageResCracker.
page_server_reads	bigint	Applies to: Azure SQL Database Hyperscale Number of page server reads performed by this request. isn't nullable.

Remarks

To execute code that is outside SQL Server (for example, extended stored procedures and distributed queries), a thread has to execute outside the control of the non-preemptive scheduler. To do this, a worker switches to preemptive mode. Time values returned by this dynamic management view don't include time spent in preemptive mode.

When executing parallel requests in row mode, SQL Server assigns a worker thread to coordinate the worker threads responsible for completing tasks assigned to them. In this DMV, only the coordinator thread is visible for the request. The columns reads, writes, logical_reads, and row_count are not updated for the coordinator thread. The columns wait_type, wait_time, last_wait_type, wait_resource, and granted_query_memory are only updated for the coordinator thread. For more information, see the Thread and Task Architecture Guide.

Permissions

If the user has VIEW SERVER STATE permission on the server, the user will see all executing sessions on the instance of SQL Server; otherwise, the user will see only the current session. VIEW SERVER STATE can't be granted in Azure SQL Database so sys.dm_exec_requests is always limited to the current connection.

In Always-On scenarios, if the secondary replica is set to read-intent only, the connection to the secondary must specify its application intent in connection string parameters by adding applicationintent=readonly. Otherwise, the access check for sys.dm_exec_requests won't pass for databases in the availability group, even if VIEW SERVER STATE permission is present.

Permissions for SQL Server 2022 and later

Requires VIEW SERVER PERFORMANCE STATE permission on the server.

Examples

A. Finding the query text for a running batch

The following example queries sys.dm_exec_requests to find the interesting query and copy its sql_handle from the output.

SELECT * FROM sys.dm_exec_requests;  
GO

Then, to obtain the statement text, use the copied sql_handle with system function sys.dm_exec_sql_text(sql_handle).

SELECT * FROM sys.dm_exec_sql_text(< copied sql_handle >);  
GO

B. Finding all locks that a running batch is holding

The following example queries sys.dm_exec_requests to find the interesting batch and copy its transaction_id from the output.

SELECT * FROM sys.dm_exec_requests;  
GO

Then, to find lock information, use the copied transaction_id with the system function sys.dm_tran_locks.

SELECT * FROM sys.dm_tran_locks
WHERE request_owner_type = N'TRANSACTION'
    AND request_owner_id = < copied transaction_id >;
GO

C. Finding all currently blocked requests

The following example queries sys.dm_exec_requests to find information about blocked requests.

SELECT session_id, status, blocking_session_id  
    , wait_type, wait_time, wait_resource
    , transaction_id
FROM sys.dm_exec_requests
WHERE status = N'suspended';  
GO

D. Ordering existing requests by CPU

SELECT 
   req.session_id
   , req.start_time
   , cpu_time 'cpu_time_ms'
   , object_name(st.objectid,st.dbid) 'ObjectName' 
   , substring
      (REPLACE
        (REPLACE
          (SUBSTRING
            (ST.text
            , (req.statement_start_offset/2) + 1
            , (
               (CASE statement_end_offset
                  WHEN -1
                  THEN DATALENGTH(ST.text)  
                  ELSE req.statement_end_offset
                  END
                    - req.statement_start_offset)/2) + 1)
       , CHAR(10), ' '), CHAR(13), ' '), 1, 512)  AS statement_text  
FROM sys.dm_exec_requests AS req  
   CROSS APPLY sys.dm_exec_sql_text(req.sql_handle) as ST
   ORDER BY cpu_time desc;
GO

Next steps

Understand and resolve SQL Server blocking problems