SQL Server wait problems [closed]

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In my production SQL Server 2012 (Standard), top 4 waits are:

1. CXPACKET
2. SOS_SCHEDULER_YIELD
3. LATCH_EX
4. WRITELOG.

And:

• MAXDOP :0
• Cost Threshold for Parallelism: 5

I know here, parallelism is screwed up here. But I would like to know proper way to diagnose the root cause and then step by step procedure to resolve it?

Answer 1

Change your Cost Thereshold to 50 to start.

Do you know how many cores per numa nodes you have? Start with that for your maxdop. If not look up the queries that Glenn Berry at SQL Skills put together.

-- SQL Server NUMA Node information  (Query 12) (SQL Server NUMA Info)
SELECT node_id, node_state_desc, memory_node_id, processor_group, cpu_count, online_scheduler_count, 
       idle_scheduler_count, active_worker_count, avg_load_balance, resource_monitor_state
FROM sys.dm_os_nodes WITH (NOLOCK) 
WHERE node_state_desc <> N'ONLINE DAC' OPTION (RECOMPILE);

He also has one for wait states

-- Isolate top waits for server instance since last restart or wait statistics clear  (Query 35) (Top Waits)
WITH [Waits] 
AS (SELECT wait_type, wait_time_ms/ 1000.0 AS [WaitS],
          (wait_time_ms - signal_wait_time_ms) / 1000.0 AS [ResourceS],
           signal_wait_time_ms / 1000.0 AS [SignalS],
           waiting_tasks_count AS [WaitCount],
           100.0 *  wait_time_ms / SUM (wait_time_ms) OVER() AS [Percentage],
           ROW_NUMBER() OVER(ORDER BY wait_time_ms DESC) AS [RowNum]
    FROM sys.dm_os_wait_stats WITH (NOLOCK)
    WHERE [wait_type] NOT IN (
        N'BROKER_EVENTHANDLER', N'BROKER_RECEIVE_WAITFOR', N'BROKER_TASK_STOP',
        N'BROKER_TO_FLUSH', N'BROKER_TRANSMITTER', N'CHECKPOINT_QUEUE',
        N'CHKPT', N'CLR_AUTO_EVENT', N'CLR_MANUAL_EVENT', N'CLR_SEMAPHORE',
        N'DBMIRROR_DBM_EVENT', N'DBMIRROR_EVENTS_QUEUE', N'DBMIRROR_WORKER_QUEUE',
        N'DBMIRRORING_CMD', N'DIRTY_PAGE_POLL', N'DISPATCHER_QUEUE_SEMAPHORE',
        N'EXECSYNC', N'FSAGENT', N'FT_IFTS_SCHEDULER_IDLE_WAIT', N'FT_IFTSHC_MUTEX',
        N'HADR_CLUSAPI_CALL', N'HADR_FILESTREAM_IOMGR_IOCOMPLETION', N'HADR_LOGCAPTURE_WAIT', 
        N'HADR_NOTIFICATION_DEQUEUE', N'HADR_TIMER_TASK', N'HADR_WORK_QUEUE',
        N'KSOURCE_WAKEUP', N'LAZYWRITER_SLEEP', N'LOGMGR_QUEUE', N'ONDEMAND_TASK_QUEUE',
        N'PREEMPTIVE_OS_QUERYREGISTRY', 
        N'PREEMPTIVE_HADR_LEASE_MECHANISM', N'PREEMPTIVE_SP_SERVER_DIAGNOSTICS',
        N'PWAIT_ALL_COMPONENTS_INITIALIZED', 
        N'QDS_PERSIST_TASK_MAIN_LOOP_SLEEP',
        N'QDS_CLEANUP_STALE_QUERIES_TASK_MAIN_LOOP_SLEEP', N'REQUEST_FOR_DEADLOCK_SEARCH',
        N'RESOURCE_QUEUE', N'SERVER_IDLE_CHECK', N'SLEEP_BPOOL_FLUSH', N'SLEEP_DBSTARTUP',
        N'SLEEP_DCOMSTARTUP', N'SLEEP_MASTERDBREADY', N'SLEEP_MASTERMDREADY',
        N'SLEEP_MASTERUPGRADED', N'SLEEP_MSDBSTARTUP', N'SLEEP_SYSTEMTASK', N'SLEEP_TASK',
        N'SLEEP_TEMPDBSTARTUP', N'SNI_HTTP_ACCEPT', N'SP_SERVER_DIAGNOSTICS_SLEEP',
        N'SQLTRACE_BUFFER_FLUSH', N'SQLTRACE_INCREMENTAL_FLUSH_SLEEP', N'SQLTRACE_WAIT_ENTRIES',
        N'WAIT_FOR_RESULTS', N'WAITFOR', N'WAITFOR_TASKSHUTDOWN', N'WAIT_XTP_HOST_WAIT',
        N'WAIT_XTP_OFFLINE_CKPT_NEW_LOG', N'WAIT_XTP_CKPT_CLOSE', N'XE_DISPATCHER_JOIN',
        N'XE_DISPATCHER_WAIT', N'XE_TIMER_EVENT')
    AND waiting_tasks_count > 0)
SELECT
    MAX (W1.wait_type) AS [WaitType],
    CAST (MAX (W1.Percentage) AS DECIMAL (5,2)) AS [Wait Percentage],
    CAST ((MAX (W1.WaitS) / MAX (W1.WaitCount)) AS DECIMAL (16,4)) AS [AvgWait_Sec],
    CAST ((MAX (W1.ResourceS) / MAX (W1.WaitCount)) AS DECIMAL (16,4)) AS [AvgRes_Sec],
    CAST ((MAX (W1.SignalS) / MAX (W1.WaitCount)) AS DECIMAL (16,4)) AS [AvgSig_Sec], 
    CAST (MAX (W1.WaitS) AS DECIMAL (16,2)) AS [Wait_Sec],
    CAST (MAX (W1.ResourceS) AS DECIMAL (16,2)) AS [Resource_Sec],
    CAST (MAX (W1.SignalS) AS DECIMAL (16,2)) AS [Signal_Sec],
    MAX (W1.WaitCount) AS [Wait Count],
    CAST (N'https://www.sqlskills.com/help/waits/' + W1.wait_type AS XML) AS [Help/Info URL]
FROM Waits AS W1
INNER JOIN Waits AS W2
ON W2.RowNum <= W1.RowNum
GROUP BY W1.RowNum, W1.wait_type
HAVING SUM (W2.Percentage) - MAX (W1.Percentage) < 99 -- percentage threshold
OPTION (RECOMPILE);

There are links to Paul Randal at SQL Skills for information about your wait states.