You should find that which of wait events are in the SQL Server database and status of currently waiting tasks.
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To solve slowness of SQL Server database, you should find which wait events exists in the database.
You can get list and status of currently waiting tasks with following script.
select wt.session_id, wt.exec_context_id, wt.wait_duration_ms, wt.wait_type, wt.blocking_session_id, wt.resource_address, wt.resource_description, s.program_name, st.text, sp.query_plan, s.cpu_time cpu_time_ms, s.memory_usage*8 memory_usage_kb from sys.dm_os_waiting_tasks wt join sys.dm_exec_sessions s on s.session_id=wt.session_id join sys.dm_exec_requests r on r.session_id=s.session_id outer apply sys.dm_exec_sql_text(r.sql_handle) st outer apply sys.dm_exec_query_plan(r.plan_handle) sp where s.is_user_process=1 order by wt.session_id, wt.exec_context_id;