SQL server 备份job堵塞查询

SELECT req.session_id, 
	database_name = db_name(req.database_id),
	req.status,
	req.blocking_session_id, 
	req.command,
	[sql_text] = Substring(txt.TEXT, (req.statement_start_offset / 2) + 1, (
				(
					CASE req.statement_end_offset
						WHEN - 1 THEN Datalength(txt.TEXT)
						ELSE req.statement_end_offset
					END - req.statement_start_offset
					) / 2
				) + 1),
	req.percent_complete,
	req.start_time,
	cpu_time_sec = req.cpu_time / 1000,
	granted_query_memory_mb = CONVERT(NUMERIC(8, 2), req.granted_query_memory / 128.),
	req.reads,
	req.logical_reads,
	req.writes,
	eta_completion_time = DATEADD(ms, req.[estimated_completion_time], GETDATE()),
	elapsed_min = CONVERT(NUMERIC(6, 2), req.[total_elapsed_time] / 1000.0 / 60.0),
	remaning_eta_min = CONVERT(NUMERIC(6, 2), req.[estimated_completion_time] / 1000.0 / 60.0),
	eta_hours = CONVERT(NUMERIC(6, 2), req.[estimated_completion_time] / 1000.0 / 60.0/ 60.0),
	wait_type,
	wait_time_sec = wait_time/1000, 
	wait_resource
FROM sys.dm_exec_requests as req WITH(NOLOCK)
	CROSS APPLY sys.dm_exec_sql_text(req.sql_handle) as txt 
WHERE req.session_id>50
	AND command IN ('BACKUP DATABASE', 'BACKUP LOG', 'RESTORE DATABASE', 'RESTORE LOG');