轉:SQL SERVER佔用CPU過高排查和優化

操作系統是Windows2008R2 ,數據庫是SQL2014 64位。

　　近階段服務器出現過幾次死機，管理員反饋機器內存使用率100%導致機器卡死。

 

　　SQL優化方法：

　　1、查看連接對象

1 USE master
2 GO
3 --如果要指定數據庫就把註釋去掉
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件，找到這臺主機並解決連接問題。在360流量防火牆中查看有哪個軟件連接了服務器IP，除之。

2、然後使用下面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爲空。

SELECT TOP 10
[session_id],
[request_id],
[start_time] AS '開始時間',
[status] AS '狀態',
[command] AS '命令',
dest.[text] AS 'sql語句', 
DB_NAME([database_id]) AS '數據庫名',
[blocking_session_id] AS '正在阻塞其他會話的會話ID',
[wait_type] AS '等待資源類型',
[wait_time] AS '等待時間',
[wait_resource] AS '等待的資源',
[reads] AS '物理讀次數',
[writes] AS '寫次數',
[logical_reads] AS '邏輯讀次數',
[row_count] AS '返回結果行數'
FROM sys.[dm_exec_requests] AS der 
CROSS APPLY 
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest 
WHERE [session_id]>50 AND DB_NAME(der.[database_id])='gposdb'  
ORDER BY [cpu_time] DESC

查看是哪些SQL語句佔用較大可以使用下面代碼

 

--在SSMS裏選擇以文本格式顯示結果
SELECT TOP 10 
dest.[text] AS 'sql語句'
FROM sys.[dm_exec_requests] AS der 
CROSS APPLY 
sys.[dm_exec_sql_text](der.[sql_handle]) AS dest 
WHERE [session_id]>50  
ORDER BY [cpu_time] DESC

 

 

 

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

SELECT TOP 10
 [session_id],
 [request_id],
 [start_time] AS '開始時間',
 [status] AS '狀態',
 [command] AS '命令',
 dest.[text] AS 'sql語句', 
 DB_NAME([database_id]) AS '數據庫名',
 [blocking_session_id] AS '正在阻塞其他會話的會話ID',
 der.[wait_type] AS '等待資源類型',
 [wait_time] AS '等待時間',
 [wait_resource] AS '等待的資源',
 [dows].[waiting_tasks_count] AS '當前正在進行等待的任務數',
 [reads] AS '物理讀次數',
 [writes] AS '寫次數',
 [logical_reads] AS '邏輯讀次數',
 [row_count] AS '返回結果行數'
 FROM sys.[dm_exec_requests] AS der 
 INNER JOIN [sys].[dm_os_wait_stats] AS dows 
 ON der.[wait_type]=[dows].[wait_type]
 CROSS APPLY 
 sys.[dm_exec_sql_text](der.[sql_handle]) AS dest 
 WHERE [session_id]>50  
 ORDER BY [cpu_time] DESC

4、查詢CPU佔用最高的SQL語句
 

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

5、索引缺失查詢

SELECT 
    DatabaseName = DB_NAME(database_id)
    ,[Number Indexes Missing] = count(*) 
FROM sys.dm_db_missing_index_details
GROUP BY DB_NAME(database_id)
ORDER BY 2 DESC;
SELECT  TOP 10 
        [Total Cost]  = ROUND(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans),0) 
        , avg_user_impact
        , TableName = statement
        , [EqualityUsage] = equality_columns 
        , [InequalityUsage] = inequality_columns
        , [Include Cloumns] = included_columns
FROM        sys.dm_db_missing_index_groups g 
INNER JOIN    sys.dm_db_missing_index_group_stats s 
       ON s.group_handle = g.index_group_handle 
INNER JOIN    sys.dm_db_missing_index_details d 
       ON d.index_handle = g.index_handle
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。