sys.dm_exec_requests (Transact-SQL)

Artykuł
12/08/2014

Returns information about each request that is executing within SQL Server.

[!UWAGA]

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 do not include time spent in preemptive mode.

Column name	Data type	Description
session_id	smallint	ID of the session to which this request is related. Is not nullable.
request_id	int	ID of the request. Unique in the context of the session. Is not nullable.
start_time	datetime	Timestamp when the request arrived. Is not nullable.
status	nvarchar(30)	Status of the request. This can be of the following: Background Running Runnable Sleeping Suspended Is not nullable.
command	nvarchar(32)	Identifies the current type of command that is being processed. Common command types include the following: 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: LOCK MONITOR CHECKPOINTLAZY WRITER Is not nullable.
sql_handle	varbinary(64)	Hash map of the SQL text of the request. Is nullable.
statement_start_offset	int	Number of characters into the currently executing batch or stored procedure at which the currently executing statement starts. 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	Number of characters into the currently executing batch or stored procedure at which the currently executing statement ends. 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.
plan_handle	varbinary(64)	Hash map of the plan for SQL execution. Is nullable.
database_id	smallint	ID of the database the request is executing against. Is not nullable.
user_id	int	ID of the user who submitted the request. Is not 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, the request is not blocked, or the session information of the blocking session is not available (or cannot be identified). -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 could not be determined at this time because of internal latch state transitions.
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. Is not nullable.
last_wait_type	nvarchar(60)	If this request has previously been blocked, this column returns the type of the last wait. Is not nullable.
wait_resource	nvarchar(256)	If the request is currently blocked, this column returns the resource for which the request is currently waiting. Is not nullable.
open_transaction_count	int	Number of transactions that are open for this request. Is not nullable.
open_resultset_count	int	Number of result sets that are open for this request. Is not nullable.
transaction_id	bigint	ID of the transaction in which this request executes. Is not 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 Is not nullable.
estimated_completion_time	bigint	Internal only. Is not nullable.
cpu_time	int	CPU time in milliseconds that is used by the request. Is not nullable.
total_elapsed_time	int	Total time elapsed in milliseconds since the request arrived. Is not nullable.
scheduler_id	int	ID of the scheduler that is scheduling this request. Is not 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. Is not nullable.
writes	bigint	Number of writes performed by this request. Is not nullable.
logical_reads	bigint	Number of logical reads that have been performed by the request. Is not nullable.
text_size	int	TEXTSIZE setting for this request. Is not 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. Is not nullable.
quoted_identifier	bit	1 = QUOTED_IDENTIFIER is ON for the request. Otherwise, it is 0. Is not nullable.
arithabort	bit	1 = ARITHABORT setting is ON for the request. Otherwise, it is 0. Is not nullable.
ansi_null_dflt_on	bit	1 = ANSI_NULL_DFLT_ON setting is ON for the request. Otherwise, it is 0. Is not nullable.
ansi_defaults	bit	1 = ANSI_DEFAULTS setting is ON for the request. Otherwise, it is 0. Is not nullable.
ansi_warnings	bit	1 = ANSI_WARNINGS setting is ON for the request. Otherwise, it is 0. Is not nullable.
ansi_padding	bit	1 = ANSI_PADDING setting is ON for the request. Otherwise, it is 0. Is not nullable.
ansi_nulls	bit	1 = ANSI_NULLS setting is ON for the request. Otherwise, it is 0. Is not nullable.
concat_null_yields_null	bit	1 = CONCAT_NULL_YIELDS_NULL setting is ON for the request. Otherwise, it is 0. Is not nullable.
transaction_isolation_level	smallint	Isolation level with which the transaction for this request is created. Is 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. Is not nullable.
deadlock_priority	int	DEADLOCK_PRIORITY setting for the request. Is not nullable.
row_count	bigint	Number of rows that have been returned to the client by this request. Is not nullable.
prev_error	int	Last error that occurred during the execution of the request. Is not nullable.
nest_level	int	Current nesting level of code that is executing on the request. Is not nullable.
granted_query_memory	int	Number of pages allocated to the execution of a query on the request. Is 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 is set for the full time a common language runtime object is on the stack, even while running Transact-SQL from within common language runtime. Is not nullable.
group_id	int	ID of the workload group to which this query belongs. Is 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.

Permissions

Requires VIEW SERVER STATE permission on the server.

[!UWAGA]

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.

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