sys.dm_exec_requests (Transact-SQL)

Άρθρο
10/04/2023

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric

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 or Microsoft Fabric use sys.dm_exec_requests.

Column name	Data type	Description
`session_id`	smallint	ID of the session to which this request is related. Not nullable.
`request_id`	int	ID of the request. Unique in the context of the session. Not nullable.
`start_time`	datetime	Timestamp when the request arrived. Not nullable.
`status`	nvarchar(30)	Status of the request. Can be one of the following values: background rollback running runnable sleeping suspended Not 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 Not nullable.
`sql_handle`	varbinary(64)	Is a token that uniquely identifies the batch or stored procedure that the query is part of. 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. 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. Nullable.
`plan_handle`	varbinary(64)	Is a token that uniquely identifies a query execution plan for a batch that is currently executing. Nullable.
`database_id`	smallint	ID of the database the request is executing against. Not nullable. In Azure SQL Database, the values are unique within a single database or an elastic pool, but not within a logical server.
`user_id`	int	ID of the user who submitted the request. Not nullable.
`connection_id`	uniqueidentifier	ID of the connection on which the request arrived. Nullable.
`blocking_session_id`	smallint	ID of the session that is blocking the request. If this column is `NULL` or `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 `blocking_session_id = -5` may be a common occurrence.
`wait_type`	nvarchar(60)	If the request is currently blocked, this column returns the type of wait. 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. Not nullable.
`last_wait_type`	nvarchar(60)	If this request has previously been blocked, this column returns the type of the last wait. Not nullable.
`wait_resource`	nvarchar(256)	If the request is currently blocked, this column returns the resource for which the request is currently waiting. Not nullable.
`open_transaction_count`	int	Number of transactions that are open for this request. Not nullable.
`open_resultset_count`	int	Number of result sets that are open for this request. Not nullable.
`transaction_id`	bigint	ID of the transaction in which this request executes. Not nullable.
`context_info`	varbinary(128)	CONTEXT_INFO value of the session. 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` Not nullable.
`estimated_completion_time`	bigint	Internal only. Not nullable.
`cpu_time`	int	CPU time in milliseconds that is used by the request. Not nullable.
`total_elapsed_time`	int	Total time elapsed in milliseconds since the request arrived. Not nullable.
`scheduler_id`	int	ID of the scheduler that is scheduling this request. Nullable.
`task_address`	varbinary(8)	Memory address allocated to the task that is associated with this request. Nullable.
`reads`	bigint	Number of reads performed by this request. Not nullable.
`writes`	bigint	Number of writes performed by this request. Not nullable.
`logical_reads`	bigint	Number of logical reads that have been performed by the request. Not nullable.
`text_size`	int	TEXTSIZE setting for this request. Not nullable.
`language`	nvarchar(128)	Language setting for the request. Nullable.
`date_format`	nvarchar(3)	DATEFORMAT setting for the request. Nullable.
`date_first`	smallint	DATEFIRST setting for the request. Not nullable.
`quoted_identifier`	bit	1 = QUOTED_IDENTIFIER is ON for the request. Otherwise, it's 0. Not nullable.
`arithabort`	bit	1 = ARITHABORT setting is ON for the request. Otherwise, it's 0. Not nullable.
`ansi_null_dflt_on`	bit	1 = ANSI_NULL_DFLT_ON setting is ON for the request. Otherwise, it's 0. Not nullable.
`ansi_defaults`	bit	1 = ANSI_DEFAULTS setting is ON for the request. Otherwise, it's 0. Not nullable.
`ansi_warnings`	bit	1 = ANSI_WARNINGS setting is ON for the request. Otherwise, it's 0. Not nullable.
`ansi_padding`	bit	1 = ANSI_PADDING setting is ON for the request. Otherwise, it's 0. Not nullable.
`ansi_nulls`	bit	1 = ANSI_NULLS setting is ON for the request. Otherwise, it's 0. Not nullable.
`concat_null_yields_null`	bit	1 = CONCAT_NULL_YIELDS_NULL setting is ON for the request. Otherwise, it's 0. Not nullable.
`transaction_isolation_level`	smallint	Isolation level with which the transaction for this request is created. Not 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. Not nullable.
`deadlock_priority`	int	DEADLOCK_PRIORITY setting for the request. Not nullable.
`row_count`	bigint	Number of rows that have been returned to the client by this request. Not nullable.
`prev_error`	int	Last error that occurred during the execution of the request. Not nullable.
`nest_level`	int	Current nesting level of code that is executing on the request. Not nullable.
`granted_query_memory`	int	Number of pages allocated to the execution of a query on the request. Not 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. Not nullable.
`group_id`	int	ID of the workload group to which this query belongs. Not 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. Not nullable.
`dist_statement_id`	uniqueidentifier	Applies to: SQL Server 2022 and later versions, Azure SQL Database, Azure SQL Managed Instance, Azure Synapse Analytics (serverless pools only), and Microsoft Fabric Unique ID for the statement for the request submitted. Not 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.

The wait_resource column contains similar information to resource_description in sys.dm_tran_locks (Transact-SQL) but is formatted differently.

Permissions

If the user has VIEW SERVER STATE permission on the server, the user sees all executing sessions on the instance of SQL Server; otherwise, the user sees 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 availability group 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 doesn't pass for databases in the availability group, even if VIEW SERVER STATE permission is present.

For SQL Server 2022 (16.x) and later versions, sys.dm_exec_requests requires VIEW SERVER PERFORMANCE STATE permission on the server.

Examples

A. Find 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. Find 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. Find 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. Order existing requests by CPU

SELECT
    [req].[session_id],
    [req].[start_time],
    [req].[cpu_time] AS [cpu_time_ms],
    OBJECT_NAME([ST].[objectid], [ST].[dbid]) AS [ObjectName],
    SUBSTRING(
        REPLACE(
            REPLACE(
                SUBSTRING(
                    [ST].[text], ([req].[statement_start_offset] / 2) + 1,
                    ((CASE [req].[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
    [req].[cpu_time] DESC;
GO

Κοινή χρήση μέσω

sys.dm_exec_requests (Transact-SQL)

Remarks

Permissions

Examples

A. Find the query text for a running batch

B. Find all locks that a running batch is holding

C. Find all currently blocked requests

D. Order existing requests by CPU

Σχόλια

Πρόσθετοι πόροι

Κοινή χρήση μέσω

sys.dm_exec_requests (Transact-SQL)

Remarks

Permissions

Examples

A. Find the query text for a running batch

B. Find all locks that a running batch is holding

C. Find all currently blocked requests

D. Order existing requests by CPU

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Σχόλια

Πρόσθετοι πόροι