SQL SERVER占用CPU过高优化

　　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

 SELECT * FROM sys.[sysprocesses] WHERE [spid]>50 --AND DB_NAME([dbid])='gposdb'

select client_net_address '客户端IP',local_net_address '服务器的IP',* from sys.dm_exec_connections

　　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。

巴特西

SQL SERVER占用CPU过高优化

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