使用DMV和DMF分析数据库性能
服务器等待的原因
SELECT TOP 10
[Wait type] = wait_type,
[Wait time (s)] = wait_time_ms / 1000,
[% waiting] = CONVERT(DECIMAL(12,2), wait_time_ms * 100.0
/ SUM(wait_time_ms) OVER())
FROM sys.dm_os_wait_stats
WHERE wait_type NOT LIKE '%SLEEP%'
ORDER BY wait_time_ms DESC;
读和写
SELECT TOP 10
[Total Reads] = SUM(total_logical_reads)
,[Execution count] = SUM(qs.execution_count)
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
GROUP BY DB_NAME(qt.dbid)
ORDER BY [Total Reads] DESC;
SELECT TOP 10
[Total Writes] = SUM(total_logical_writes)
,[Execution count] = SUM(qs.execution_count)
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
GROUP BY DB_NAME(qt.dbid)
ORDER BY [Total Writes] DESC;
数据库缺失索引
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;
缺失索引列表信息
SELECT DatabaseName = DB_NAME(database_id),* FROM sys.dm_db_missing_index_details Order BY DB_NAME(database_id)
高开销的缺失索引
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;
确定开销最高的未使用索引
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;
确定最高开销索引所使用的脚本并显示结果。
-- Create required table structure only.
-- Note: this SQL must be the same as in the Database loop given in the following step.
SELECT TOP 1
[Maintenance cost] = (user_updates + system_updates)
,[Retrieval usage] = (user_seeks + user_scans + user_lookups)
,DatabaseName = DB_NAME()
,TableName = OBJECT_NAME(s.[object_id])
,IndexName = i.name
INTO #TempMaintenanceCost
FROM sys.dm_db_index_usage_stats s
INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
AND s.index_id = i.index_id
WHERE s.database_id = DB_ID()
AND OBJECTPROPERTY(s.[object_id], 'IsMsShipped') = 0
AND (user_updates + system_updates) > 0 -- Only report on active rows.
AND s.[object_id] = -999 -- Dummy value to get table structure.
;
-- Loop around all the databases on the server.
EXEC sp_MSForEachDB 'USE [?];
-- Table already exists.
INSERT INTO #TempMaintenanceCost
SELECT TOP 10
[Maintenance cost] = (user_updates + system_updates)
,[Retrieval usage] = (user_seeks + user_scans + user_lookups)
,DatabaseName = DB_NAME()
,TableName = OBJECT_NAME(s.[object_id])
,IndexName = i.name
FROM sys.dm_db_index_usage_stats s
INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
AND s.index_id = i.index_id
WHERE s.database_id = DB_ID()
AND i.name IS NOT NULL -- Ignore HEAP indexes.
AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0
AND (user_updates + system_updates) > 0 -- Only report on active rows.
ORDER BY [Maintenance cost] DESC
;
'
-- Select records.
SELECT TOP 10 * FROM #TempMaintenanceCost
ORDER BY [Maintenance cost] DESC
-- Tidy up.
DROP TABLE #TempMaintenanceCost
显示索引已被使用的次数，并按“使用率”排序。
-- Create required table structure only.
-- Note: this SQL must be the same as in the Database loop given in the -- following step.
SELECT TOP 1
[Usage] = (user_seeks + user_scans + user_lookups)
,DatabaseName = DB_NAME()
,TableName = OBJECT_NAME(s.[object_id])
,IndexName = i.name
INTO #TempUsage
FROM sys.dm_db_index_usage_stats s
INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
AND s.index_id = i.index_id
WHERE s.database_id = DB_ID()
AND OBJECTPROPERTY(s.[object_id], 'IsMsShipped') = 0
AND (user_seeks + user_scans + user_lookups) > 0
-- Only report on active rows.
AND s.[object_id] = -999 -- Dummy value to get table structure.
;
-- Loop around all the databases on the server.
EXEC sp_MSForEachDB 'USE [?];
-- Table already exists.
INSERT INTO #TempUsage
SELECT TOP 10
[Usage] = (user_seeks + user_scans + user_lookups)
,DatabaseName = DB_NAME()
,TableName = OBJECT_NAME(s.[object_id])
,IndexName = i.name
FROM sys.dm_db_index_usage_stats s
INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
AND s.index_id = i.index_id
WHERE s.database_id = DB_ID()
AND i.name IS NOT NULL -- Ignore HEAP indexes.
AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0
AND (user_seeks + user_scans + user_lookups) > 0 -- Only report on active rows.
ORDER BY [Usage] DESC
;
'
-- Select records.
SELECT TOP 10 * FROM #TempUsage ORDER BY [Usage] DESC
-- Tidy up.
DROP TABLE #TempUsage
逻辑上最零碎的索引所使用的脚本
-- Create required table structure only.
-- Note: this SQL must be the same as in the Database loop given in the -- following step.
SELECT TOP 1
DatbaseName = DB_NAME()
,TableName = OBJECT_NAME(s.[object_id])
,IndexName = i.name
,[Fragmentation %] = ROUND(avg_fragmentation_in_percent,2)
INTO #TempFragmentation
FROM sys.dm_db_index_physical_stats(db_id(),null, null, null, null) s
INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
AND s.index_id = i.index_id
WHERE s.[object_id] = -999 -- Dummy value just to get table structure.
;
-- Loop around all the databases on the server.
EXEC sp_MSForEachDB 'USE [?];
-- Table already exists.
INSERT INTO #TempFragmentation
SELECT TOP 10
DatbaseName = DB_NAME()
,TableName = OBJECT_NAME(s.[object_id])
,IndexName = i.name
,[Fragmentation %] = ROUND(avg_fragmentation_in_percent,2)
FROM sys.dm_db_index_physical_stats(db_id(),null, null, null, null) s
INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
AND s.index_id = i.index_id
WHERE s.database_id = DB_ID()
AND i.name IS NOT NULL -- Ignore HEAP indexes.
AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0
ORDER BY [Fragmentation %] DESC
;
'
-- Select records.
SELECT TOP 10 * FROM #TempFragmentation ORDER BY [Fragmentation %] DESC
-- Tidy up.
DROP TABLE #TempFragmentation
获得IO高的查询
SELECT TOP 10
[Average IO] = (total_logical_reads + total_logical_writes) / qs.execution_count
,[Total IO] = (total_logical_reads + total_logical_writes)
,[Execution count] = qs.execution_count
,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
,[Parent Query] = qt.text
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
ORDER BY [Average IO] DESC;
获得I/O统计
Select wait_type, waiting_tasks_count, wait_time_ms from sys.dm_os_wait_stats where wait_type like 'PAGEIOLATCH%' order by wait_type
查询当前I/O锁
select DB_NAME(database_id), file_id, io_stall,io_pending_ms_ticks,scheduler_address from sys.dm_io_virtual_file_stats(NULL, NULL) t1,sys.dm_io_pending_io_requests as t2 where t1.file_handle = t2.io_handle
看是那5条语句导致I/O高
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
根据句柄得到语句
select text from sys.dm_exec_sql_text(0x03000E00D4AB884E808214016B9A00000100000000000000)
查询可以确定按 CPU 使用率衡量的、开销最高的查询
SELECT TOP 10
[Average CPU used] = total_worker_time / qs.execution_count
,[Total CPU used] = total_worker_time
,[Execution count] = qs.execution_count
,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
ELSE qs.statement_end_offset END -
qs.statement_start_offset)/2)
,[Parent Query] = qt.text
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
ORDER BY [Average CPU used] DESC;
高开销的 CLR 查询
SELECT TOP 10
[Average CLR Time] = total_clr_time / execution_count
,[Total CLR Time] = total_clr_time
,[Execution count] = qs.execution_count
,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
,[Parent Query] = qt.text
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats as qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
WHERE total_clr_time <> 0
ORDER BY [Average CLR Time] DESC;
最常执行的查询
SELECT TOP 10
[Execution count] = execution_count
,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
,[Parent Query] = qt.text
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
ORDER BY [Execution count] DESC;
受阻塞影响的查询
SELECT TOP 10
[Average Time Blocked] = (total_elapsed_time - total_worker_time) / qs.execution_count
,[Total Time Blocked] = total_elapsed_time - total_worker_time
,[Execution count] = qs.execution_count
,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
,[Parent Query] = qt.text
,DatabaseName = DB_NAME(qt.dbid)
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
ORDER BY [Average Time Blocked] DESC;
最低计划重用率
SELECT TOP 100
[Plan usage] = cp.usecounts
,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX),
qt.text)) * 2 ELSE qs.statement_end_offset END -
qs.statement_start_offset)/2)
,[Parent Query] = qt.text
,DatabaseName = DB_NAME(qt.dbid)
,cp.cacheobjtype
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) AS qt
INNER JOIN sys.dm_exec_cached_plans as cp on qs.plan_handle=cp.plan_handle
WHERE cp.plan_handle=qs.plan_handle
ORDER BY [Plan usage] ASC;
数据库连接情况
SELECT session_id,connect_time,endpoint_id,auth_scheme,num_reads,num_writes,client_net_address,connection_id from sys.dm_exec_connections order by client_net_address
查询优化器信息
select * from sys.dm_exec_query_optimizer_info
当前执行请求
select * from sys.dm_exec_requests
当前执行session
select * from sys.dm_exec_sessions
所有的调度器并产看等待运行的任务数量
select
scheduler_id,
current_tasks_count,
runnable_tasks_count
from
sys.dm_os_schedulers
where
scheduler_id < 255
所有的调度器并产看等待运行的任务数量
select
*
from
sys.dm_os_schedulers
where
scheduler_id < 255
整个CPU使用中最占用资源的查询
select top 50
sum(qs.total_worker_time) as total_cpu_time,
sum(qs.execution_count) as total_execution_count,
count(*) as number_of_statements,
qs.plan_handle
from
sys.dm_exec_query_stats qs
group by qs.plan_handle
order by sum(qs.total_worker_time) desc
所有的调度器并产看等待运行的任务数量
select
scheduler_id,
current_tasks_count,
runnable_tasks_count
from
sys.dm_os_schedulers
where
scheduler_id < 255
所有的调度器并产看等待运行的任务数量
select
*
from
sys.dm_os_schedulers
where
scheduler_id < 255
整个CPU使用中最占用资源的查询
select top 50
sum(qs.total_worker_time) as total_cpu_time,
sum(qs.execution_count) as total_execution_count,
count(*) as number_of_statements,
qs.plan_handle
from
sys.dm_exec_query_stats qs
group by qs.plan_handle
order by sum(qs.total_worker_time) desc
得到在给定的时间段内花费在查询优化的时间
select * from sys.dm_exec_query_optimizer_info
重编译次数最多的25个存储过程
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
累计使用cpu最多的查询
select
highest_cpu_queries.plan_handle,
highest_cpu_queries.total_worker_time,
q.dbid,
q.objectid,
q.number,
q.encrypted,
q.[text]
from
(select top 50
qs.plan_handle,
qs.total_worker_time
from
sys.dm_exec_query_stats qs
order by qs.total_worker_time desc) as highest_cpu_queries
cross apply sys.dm_exec_sql_text(plan_handle) as q
order by highest_cpu_queries.total_worker_time desc
清空统计项的方法
checkpoint 检查点
dbcc freeproccache 释放缓存，小心
dbcc dropcleanbuffers 清空缓存，小心
DBCC SQLPERF ('sys.dm_os_wait_stats', CLEAR); 清空某一项
GO
综合分析:
SELECT DB_ID(DB.dbid) '数据库名'
, OBJECT_ID(db.objectid) '对象'
, QS.creation_time '编译计划的时间'
, QS.last_execution_time '上次执行计划的时间'
, QS.execution_count '执行的次数'
, QS.total_elapsed_time / 1000 '占用的总时间（秒）'
, QS.total_physical_reads '物理读取总次数'
, QS.total_worker_time / 1000 'CPU 时间总量（秒）'
, QS.total_logical_writes '逻辑写入总次数'
, QS.total_logical_reads N'逻辑读取总次数'
, QS.total_elapsed_time / 1000 N'总花费时间（秒）'
, SUBSTRING(ST.text, ( QS.statement_start_offset / 2 ) + 1,
( ( CASE statement_end_offset
WHEN -1 THEN DATALENGTH(st.text)
ELSE QS.statement_end_offset
END - QS.statement_start_offset ) / 2 ) + 1) AS '执行语句',
[Parent Query] = st.text
FROM sys.dm_exec_query_stats AS QS CROSS APPLY
sys.dm_exec_sql_text(QS.sql_handle) AS ST INNER JOIN
( SELECT *
FROM sys.dm_exec_cached_plans cp CROSS APPLY
sys.dm_exec_query_plan(cp.plan_handle)
) DB
ON QS.plan_handle = DB.plan_handle
where SUBSTRING(st.text, ( qs.statement_start_offset / 2 ) + 1,
( ( CASE statement_end_offset
WHEN -1 THEN DATALENGTH(st.text)
ELSE qs.statement_end_offset
END - qs.statement_start_offset ) / 2 ) + 1) not like '%fetch%'
ORDER BY QS.total_elapsed_time / 1000 DESC
