SQL SERVER占用CPU過高排查和優化

轉載自：https://www.cnblogs.com/vice/p/9163241.html

操作系統是Windows2008R2 ,資料庫是SQL2014 64位。

　　近階段伺服器出現過幾次死機，管理員反饋機器記憶體使用率100%導致機器卡死。於是做了個監測伺服器的軟體實時記錄CPU數據，幾日觀察得出數據如下：

　　SQL優化方法：

　　1、查看連接對象

1 USE master
2 GO
3 --如果要指定資料庫就把註釋去掉
4 SELECT * FROM sys.[sysprocesses] WHERE [spid]>50 --AND DB_NAME([dbid])='gposdb'

　　當前連接對象有67個其中‘WINAME’的主機名，‘jTDS’的進程名不屬於已知常用軟體，找到這台主機並解決連接問題。在360流量防火牆中查看有哪個軟體連接了伺服器IP，除之。

2、然後使用下麵語句看一下各項指標是否正常，是否有阻塞，正常情況下搜索結果應該為空。

查看是哪些SQL語句占用較大可以使用下麵代碼

3、如果SQLSERVER存在要等待的資源，那麼執行下麵語句就會顯示出會話中有多少個worker在等待

 1 SELECT TOP 10
 2  [session_id],
 3  [request_id],
 4  [start_time] AS '開始時間',
 5  [status] AS '狀態',
 6  [command] AS '命令',
 7  dest.[text] AS 'sql語句', 
 8  DB_NAME([database_id]) AS '資料庫名',
 9  [blocking_session_id] AS '正在阻塞其他會話的會話ID',
10  der.[wait_type] AS '等待資源類型',
11  [wait_time] AS '等待時間',
12  [wait_resource] AS '等待的資源',
13  [dows].[waiting_tasks_count] AS '當前正在進行等待的任務數',
14  [reads] AS '物理讀次數',
15  [writes] AS '寫次數',
16  [logical_reads] AS '邏輯讀次數',
17  [row_count] AS '返回結果行數'
18  FROM sys.[dm_exec_requests] AS der 
19  INNER JOIN [sys].[dm_os_wait_stats] AS dows 
20  ON der.[wait_type]=[dows].[wait_type]
21  CROSS APPLY 
22  sys.[dm_exec_sql_text](der.[sql_handle]) AS dest 
23  WHERE [session_id]>50  
24  ORDER BY [cpu_time] DESC

4、查詢CPU占用最高的SQL語句

 1 SELECT TOP 10
 2    total_worker_time/execution_count AS avg_cpu_cost, plan_handle,
 3    execution_count,
 4    (SELECT SUBSTRING(text, statement_start_offset/2 + 1,
 5       (CASE WHEN statement_end_offset = -1
 6          THEN LEN(CONVERT(nvarchar(max), text)) * 2
 7          ELSE statement_end_offset
 8       END - statement_start_offset)/2)
 9    FROM sys.dm_exec_sql_text(sql_handle)) AS query_text
10 FROM sys.dm_exec_query_stats
11 ORDER BY [avg_cpu_cost] DESC

5、索引缺失查詢

 1 SELECT 
 2     DatabaseName = DB_NAME(database_id)
 3     ,[Number Indexes Missing] = count(*) 
 4 FROM sys.dm_db_missing_index_details
 5 GROUP BY DB_NAME(database_id)
 6 ORDER BY 2 DESC;
 7 SELECT  TOP 10 
 8         [Total Cost]  = ROUND(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans),0) 
 9         , avg_user_impact
10         , TableName = statement
11         , [EqualityUsage] = equality_columns 
12         , [InequalityUsage] = inequality_columns
13         , [Include Cloumns] = included_columns
14 FROM        sys.dm_db_missing_index_groups g 
15 INNER JOIN    sys.dm_db_missing_index_group_stats s 
16        ON s.group_handle = g.index_group_handle 
17 INNER JOIN    sys.dm_db_missing_index_details d 
18        ON d.index_handle = g.index_handle
19 ORDER BY [Total Cost] DESC;

　　找到索引缺失的表，根據查詢結果中的關鍵次逐一建立索引。

　　做完這些測試，基本能找到問題。