SQL SERVER占用CPU过高排查和优化

操作系统是Windows2008R2 ,数据库是SQL2014 64位。

　　近阶段服务器出现过几次死机，管理员反馈机器内存使用率100%导致机器卡死。于是做了个监测服务器的软件实时记录CPU数据，几日观察得出数据如下：

　　SQL优化方法：

　　1、查看连接对象

1 USE master
2 GO
3 --如果要指定数据库就把注释去掉
4 SELECT * FROM sys.[sysprocesses] WHERE [spid]>50 --AND DB_NAME([dbid])=\'gposdb\'

　　当前连接对象有67个其中‘WINAME’的主机名，‘jTDS’的进程名不属于已知常用软件，找到这台主机并解决连接问题。在360流量防火墙中查看有哪个软件连接了服务器IP，除之。

2、然后使用下面语句看一下各项指标是否正常，是否有阻塞，正常情况下搜索结果应该为空。

1 SELECT TOP 10
 2 [session_id],
 3 [request_id],
 4 [start_time] AS \'开始时间\',
 5 [status] AS \'状态\',
 6 [command] AS \'命令\',
 7 dest.[text] AS \'sql语句\', 
 8 DB_NAME([database_id]) AS \'数据库名\',
 9 [blocking_session_id] AS \'正在阻塞其他会话的会话ID\',
10 [wait_type] AS \'等待资源类型\',
11 [wait_time] AS \'等待时间\',
12 [wait_resource] AS \'等待的资源\',
13 [reads] AS \'物理读次数\',
14 [writes] AS \'写次数\',
15 [logical_reads] AS \'逻辑读次数\',
16 [row_count] AS \'返回结果行数\'
17 FROM sys.[dm_exec_requests] AS der 
18 CROSS APPLY 
19 sys.[dm_exec_sql_text](der.[sql_handle]) AS dest 
20 WHERE [session_id]>50 AND DB_NAME(der.[database_id])=\'gposdb\'  
21 ORDER BY [cpu_time] DESC

查看是哪些SQL语句占用较大可以使用下面代码

1 --在SSMS里选择以文本格式显示结果
2 SELECT TOP 10 
3 dest.[text] AS \'sql语句\'
4 FROM sys.[dm_exec_requests] AS der 
5 CROSS APPLY 
6 sys.[dm_exec_sql_text](der.[sql_handle]) AS dest 
7 WHERE [session_id]>50  
8 ORDER BY [cpu_time] DESC

3、如果SQLSERVER存在要等待的资源，那么执行下面语句就会显示出会话中有多少个worker在等待

1 SELECT TOP 10
 2  [session_id],
 3  [request_id],
 4  [start_time] AS \'开始时间\',
 5  [status] AS \'状态\',
 6  [command] AS \'命令\',
 7  dest.[text] AS \'sql语句\', 
 8  DB_NAME([database_id]) AS \'数据库名\',
 9  [blocking_session_id] AS \'正在阻塞其他会话的会话ID\',
10  der.[wait_type] AS \'等待资源类型\',
11  [wait_time] AS \'等待时间\',
12  [wait_resource] AS \'等待的资源\',
13  [dows].[waiting_tasks_count] AS \'当前正在进行等待的任务数\',
14  [reads] AS \'物理读次数\',
15  [writes] AS \'写次数\',
16  [logical_reads] AS \'逻辑读次数\',
17  [row_count] AS \'返回结果行数\'
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、查询CPU占用最高的SQL语句

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、索引缺失查询

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，根据查询结果中的关键次逐一建立索引。

　　做完这些测试，基本能找到问题。