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

USE master

GO

--如果要指定数据库就把注释去掉

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。

SELECT TOP 10

[session_id],

[request_id],

[start_time] AS '开始时间',

[status] AS '状态',

[command] AS '命令',

dest.[text] AS 'sql语句',

DB_NAME([database_id]) AS '数据库名',

[blocking_session_id] AS '正在阻塞其他会话的会话ID',

[wait_type] AS '等待资源类型',

[wait_time] AS '等待时间',

[wait_resource] AS '等待的资源',

[reads] AS '物理读次数',

[writes] AS '写次数',

[logical_reads] AS '逻辑读次数',

[row_count] AS '返回结果行数'

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语句占用较大可以使用下面代码

--在SSMS里选择以文本格式显示结果

SELECT TOP 10

dest.[text] AS 'sql语句'

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

SELECT TOP 10

[session_id],

[request_id],

[start_time] AS '开始时间',

[status] AS '状态',

[command] AS '命令',

dest.[text] AS 'sql语句',

DB_NAME([database_id]) AS '数据库名',

[blocking_session_id] AS '正在阻塞其他会话的会话ID',

der.[wait_type] AS '等待资源类型',

[wait_time] AS '等待时间',

[wait_resource] AS '等待的资源',

[dows].[waiting_tasks_count] AS '当前正在进行等待的任务数',

[reads] AS '物理读次数',

[writes] AS '写次数',

[logical_reads] AS '逻辑读次数',

[row_count] AS '返回结果行数'

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、查询CPU占用最高的SQL语句

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、索引缺失查询

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。