监控 SQL Server (2005/2008) 的运行状况

原文地址：
http://technet.microsoft.com/zh-cn/library/bb838723.aspx

Microsoft SQL Server 2005 提供了一些工具来监控数据库。方法之一是动态管理视图。动态管理视图 (DMV) 和动态管理函数 (DMF) 返回的服务器状态信息可用于监控服务器实例的运行状况、诊断问题和优化性能。

常规服务器动态管理对象包括：

• dm_db_*：数据库和数据库对象

• dm_exec_*：执行用户代码和关联的连接

• dm_os_*：内存、锁定和时间安排

• dm_tran_*：事务和隔离

• dm_io_*：网络和磁盘的输入/输出

此部分介绍为监控 SQL Server 运行状况而针对这些动态管理视图和函数运行的一些常用查询。

摘录部分精彩SQL如下：

下面的查询显示 CPU 平均占用率最高的前 50 个 SQL 语句。

SELECT TOP 50
total_worker_time/execution_count AS [Avg CPU Time],
(SELECT SUBSTRING(text,statement_start_offset/2,(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 Time] DESC

SELECT TOP 50 total_worker_time/execution_count AS [Avg CPU Time], (SELECT SUBSTRING(text,statement_start_offset/2,(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 Time] DESC

下面的查询显示一些可能占用大量 CPU 使用率的运算符（例如 ‘%Hash Match%’、‘%Sort%’）以找出可疑对象。

select   *
from
      sys.dm_exec_cached_plans
       cross  apply sys.dm_exec_query_plan(plan_handle)
where
       cast (query_plan  as   nvarchar ( max ))  like   ' %Sort% '
       or   cast (query_plan  as   nvarchar ( max ))  like   ' %Hash Match% '

select * from sys.dm_exec_cached_plans cross apply sys.dm_exec_query_plan(plan_handle) where cast (query_plan as nvarchar ( max )) like ' %Sort% ' or cast (query_plan as nvarchar ( max )) like ' %Hash Match% '

运行下面的 DMV 查询以查看 CPU、计划程序内存和缓冲池信息。

select
cpu_count,
hyperthread_ratio,
scheduler_count,
physical_memory_in_bytes  /   1024   /   1024   as  physical_memory_mb,
virtual_memory_in_bytes  /   1024   /   1024   as  virtual_memory_mb,
bpool_committed  *   8   /   1024   as  bpool_committed_mb,
bpool_commit_target  *   8   /   1024   as  bpool_target_mb,
bpool_visible  *   8   /   1024   as  bpool_visible_mb
from  sys.dm_os_sys_info

select cpu_count, hyperthread_ratio, scheduler_count, physical_memory_in_bytes / 1024 / 1024 as physical_memory_mb, virtual_memory_in_bytes / 1024 / 1024 as virtual_memory_mb, bpool_committed * 8 / 1024 as bpool_committed_mb, bpool_commit_target * 8 / 1024 as bpool_target_mb, bpool_visible * 8 / 1024 as bpool_visible_mb from sys.dm_os_sys_info

下面的示例查询显示已重新编译的前 25 个存储过程。plan_generation_num 指示该查询已重新编译的次数。

select   top   25
sql_text. text ,
sql_handle,
plan_generation_num,
execution_count,
dbid,
objectid
from  sys.dm_exec_query_stats a
cross  apply sys.dm_exec_sql_text(sql_handle)  as  sql_text
where  plan_generation_num  >   1
order   by  plan_generation_num  desc

select top 25 sql_text. text , sql_handle, plan_generation_num, execution_count, dbid, objectid from sys.dm_exec_query_stats a cross apply sys.dm_exec_sql_text(sql_handle) as sql_text where plan_generation_num > 1 order by plan_generation_num desc

下面的 DMV 查询可用于查找哪些批处理/请求生成的 I/O 最多。如下所示的 DMV 查询可用于查找可生成最多 I/O 的前五个请求。调整这些查询将提高系统性能。

select   top   5
    (total_logical_reads / execution_count)  as  avg_logical_reads,
    (total_logical_writes / execution_count)  as  avg_logical_writes,
    (total_physical_reads / execution_count)  as  avg_phys_reads,
     Execution_count,
    statement_start_offset  as  stmt_start_offset,
    sql_handle,
    plan_handle
from  sys.dm_exec_query_stats
order   by   (total_logical_reads  +  total_logical_writes)  Desc