SQLServer数据库优化与管理——工具定位瓶颈

数据收集器集

数据收集器集可以理解为个进阶的性能监视器工具，它最常用的场景是长时间自动
收集指定数据。它不像性能监视器那样只能短暂地收集一段时间的数据，使用数据收集器，
可以进行长达数月的性能数据收集，对服务器性能评估、建立性能基线及时间段等的监控
都很有帮助，而且它是在后台运行，不需要一直开着性能监视器。

使用PAL分析

PAL可以分析通过性能数据收集器收集的文件，不需要对结果(特别是大量、长时间
收集的数据）进行人工分析。PAL的下载地址为:http://pal.codeplex.com/。下面通过一个

使用DMO 获取性能数据

DMO，动态管理对象，包括动态管理视图(DMV)）和动态管理函数(DMF)，从SQL
Server 2005开始引入，主要目的在于替代SQL Server 2000及以前版本中的系统表，并提
供更丰富的SQL Server运行信息。前面的章节中大量使用这种工具来进行信息统计及性能
问题侦测，并且在后续版本中持续加入了新的DMO。可见微软把DMO当作了一个可持续
使用的技术，并且它在日常管理、优化中具有不可替代的地位。

DMO介绍

DMO并不是实体表，从名称来说，它是动态的。这里面有两个含义，其-是大部分的
DMO 都是在执行时才汇总数据，其二是它的数据具有不稳定性，在服务器或者某些命令执
行之后，相应的数据就会被清空，同时这类数据绝大部分是累计值，并不是实时数据。所
以建议对这些数据进行周期性收集，并记录在一个专用的数据库或者其他库中，以便需要
时使用。详细的知识可以阅读《Performance Tuning with SQL Server Dynamic Management Views》一书。

索引篇

-- 未被使用的索引
SELECT  OBJECT_NAME(i.[object_id]) AS [Table Name] ,
        i.name
FROM    sys.indexes AS i
        INNER JOIN sys.objects AS o ON i.[object_id] = o.[object_id]
WHERE   i.index_id NOT IN ( SELECT  ddius.index_id
                            FROM    sys.dm_db_index_usage_stats AS ddius
                            WHERE   ddius.[object_id] = i.[object_id]
                                    AND i.index_id = ddius.index_id
                                    AND database_id = DB_ID() )
        AND o.[type] = 'U'
ORDER BY OBJECT_NAME(i.[object_id]) ASC;


--需要维护但是未被用过的索引
SELECT  '[' + DB_NAME() + '].[' + su.[name] + '].[' + o.[name] + ']' AS [statement] ,
        i.[name] AS [index_name] ,
        ddius.[user_seeks] + ddius.[user_scans] + ddius.[user_lookups] AS [user_reads] ,
        ddius.[user_updates] AS [user_writes] ,
        SUM(SP.rows) AS [total_rows]
FROM    sys.dm_db_index_usage_stats ddius
        INNER JOIN sys.indexes i ON ddius.[object_id] = i.[object_id]
                                    AND i.[index_id] = ddius.[index_id]
        INNER JOIN sys.partitions SP ON ddius.[object_id] = SP.[object_id]
                                        AND SP.[index_id] = ddius.[index_id]
        INNER JOIN sys.objects o ON ddius.[object_id] = o.[object_id]
        INNER JOIN sys.sysusers su ON o.[schema_id] = su.[UID]
WHERE   ddius.[database_id] = DB_ID() -- current database only 
        AND OBJECTPROPERTY(ddius.[object_id], 'IsUserTable') = 1
        AND ddius.[index_id] > 0
GROUP BY su.[name] ,
        o.[name] ,
        i.[name] ,
        ddius.[user_seeks] + ddius.[user_scans] + ddius.[user_lookups] ,
        ddius.[user_updates]
HAVING  ddius.[user_seeks] + ddius.[user_scans] + ddius.[user_lookups] = 0
ORDER BY ddius.[user_updates] DESC ,
        su.[name] ,
        o.[name] ,
        i.[name]


-- 可能不高效的非聚集索引 (writes > reads) 
SELECT  OBJECT_NAME(ddius.[object_id]) AS [Table Name] ,
        i.name AS [Index Name] ,
        i.index_id ,
        user_updates AS [Total Writes] ,
        user_seeks + user_scans + user_lookups AS [Total Reads] ,
        user_updates - ( user_seeks + user_scans + user_lookups ) AS [Difference]
FROM    sys.dm_db_index_usage_stats AS ddius WITH ( NOLOCK )
        INNER JOIN sys.indexes AS i WITH ( NOLOCK ) ON ddius.[object_id] = i.[object_id]
                                                       AND i.index_id = ddius.index_id
WHERE   OBJECTPROPERTY(ddius.[object_id], 'IsUserTable') = 1
        AND ddius.database_id = DB_ID()
        AND user_updates > ( user_seeks + user_scans + user_lookups )
        AND i.index_id > 1
ORDER BY [Difference] DESC ,
        [Total Writes] DESC ,
        [Total Reads] ASC;


--没有用于用户查询的索引
SELECT  '[' + DB_NAME() + '].[' + su.[name] + '].[' + o.[name] + ']' AS [statement] ,
        i.[name] AS [index_name] ,
        ddius.[user_seeks] + ddius.[user_scans] + ddius.[user_lookups] AS [user_reads] ,
        ddius.[user_updates] AS [user_writes] ,
        ddios.[leaf_insert_count] ,
        ddios.[leaf_delete_count] ,
        ddios.[leaf_update_count] ,
        ddios.[nonleaf_insert_count] ,
        ddios.[nonleaf_delete_count] ,
        ddios.[nonleaf_update_count]
FROM    sys.dm_db_index_usage_stats ddius
        INNER JOIN sys.indexes i ON ddius.[object_id] = i.[object_id]
                                    AND i.[index_id] = ddius.[index_id]
        INNER JOIN sys.partitions SP ON ddius.[object_id] = SP.[object_id]
                                        AND SP.[index_id] = ddius.[index_id]
        INNER JOIN sys.objects o ON ddius.[object_id] = o.[object_id]
        INNER JOIN sys.sysusers su ON o.[schema_id] = su.[UID]
        INNER JOIN sys.[dm_db_index_operational_stats](DB_ID(), NULL, NULL,
                                                       NULL) AS ddios ON ddius.[index_id] = ddios.[index_id]
                                                              AND ddius.[object_id] = ddios.[object_id]
                                                              AND SP.[partition_number] = ddios.[partition_number]
                                                              AND ddius.[database_id] = ddios.[database_id]
WHERE   OBJECTPROPERTY(ddius.[object_id], 'IsUserTable') = 1
        AND ddius.[index_id] > 0
        AND ddius.[user_seeks] + ddius.[user_scans] + ddius.[user_lookups] = 0
ORDER BY ddius.[user_updates] DESC ,
        su.[name] ,
        o.[name] ,
        i.[name]


--识别在行级的锁定和阻塞
SELECT  '[' + DB_NAME(ddios.[database_id]) + '].[' + su.[name] + '].['
        + o.[name] + ']' AS [statement] ,
        i.[name] AS 'index_name' ,
        ddios.[partition_number] ,
        ddios.[row_lock_count] ,
        ddios.[row_lock_wait_count] ,
        CAST (100.0 * ddios.[row_lock_wait_count] / ( ddios.[row_lock_count] ) AS DECIMAL(5,
                                                              2)) AS [%_times_blocked] ,
        ddios.[row_lock_wait_in_ms] ,
        CAST (1.0 * ddios.[row_lock_wait_in_ms] / ddios.[row_lock_wait_count] AS DECIMAL(15,
                                                              2)) AS [avg_row_lock_wait_in_ms]
FROM    sys.dm_db_index_operational_stats(DB_ID(), NULL, NULL, NULL) ddios
        INNER JOIN sys.indexes i ON ddios.[object_id] = i.[object_id]
                                    AND i.[index_id] = ddios.[index_id]
        INNER JOIN sys.objects o ON ddios.[object_id] = o.[object_id]
        INNER JOIN sys.sysusers su ON o.[schema_id] = su.[UID]
WHERE   ddios.row_lock_wait_count > 0
        AND OBJECTPROPERTY(ddios.[object_id], 'IsUserTable') = 1
        AND i.[index_id] > 0
ORDER BY ddios.[row_lock_wait_count] DESC ,
        su.[name] ,
        o.[name] ,
        i.[name]
--识别闩锁等待
SELECT  '[' + DB_NAME() + '].[' + OBJECT_SCHEMA_NAME(ddios.[object_id])
        + '].[' + OBJECT_NAME(ddios.[object_id]) + ']' AS [object_name] ,
        i.[name] AS index_name ,
        ddios.page_io_latch_wait_count ,
        ddios.page_io_latch_wait_in_ms ,
        ( ddios.page_io_latch_wait_in_ms / ddios.page_io_latch_wait_count ) AS avg_page_io_latch_wait_in_ms
FROM    sys.dm_db_index_operational_stats(DB_ID(), NULL, NULL, NULL) ddios
        INNER JOIN sys.indexes i ON ddios.[object_id] = i.[object_id]
                                    AND i.index_id = ddios.index_id
WHERE   ddios.page_io_latch_wait_count > 0
        AND OBJECTPROPERTY(i.object_id, 'IsUserTable') = 1
ORDER BY ddios.page_io_latch_wait_count DESC ,
        avg_page_io_latch_wait_in_ms DESC
--识别锁升级
SELECT  OBJECT_NAME(ddios.[object_id], ddios.database_id) AS [object_name] ,
        i.name AS index_name ,
        ddios.index_id ,
        ddios.partition_number ,
        ddios.index_lock_promotion_attempt_count ,
        ddios.index_lock_promotion_count ,
        ( ddios.index_lock_promotion_attempt_count
          / ddios.index_lock_promotion_count ) AS percent_success
FROM    sys.dm_db_index_operational_stats(DB_ID(), NULL, NULL, NULL) ddios
        INNER JOIN sys.indexes i ON ddios.object_id = i.object_id
                                    AND ddios.index_id = i.index_id
WHERE   ddios.index_lock_promotion_count > 0
ORDER BY index_lock_promotion_count DESC;
--与锁争用有关的索引
SELECT  OBJECT_NAME(ddios.object_id, ddios.database_id) AS object_name ,
        i.name AS index_name ,
        ddios.index_id ,
        ddios.partition_number ,
        ddios.page_lock_wait_count ,
        ddios.page_lock_wait_in_ms ,
        CASE WHEN DDMID.database_id IS NULL THEN 'N'
             ELSE 'Y'
        END AS missing_index_identified
FROM    sys.dm_db_index_operational_stats(DB_ID(), NULL, NULL, NULL) ddios
        INNER JOIN sys.indexes i ON ddios.object_id = i.object_id
                                    AND ddios.index_id = i.index_id
        LEFT OUTER JOIN ( SELECT DISTINCT
                                    database_id ,
                                    object_id
                          FROM      sys.dm_db_missing_index_details
                        ) AS DDMID ON DDMID.database_id = ddios.database_id
                                      AND DDMID.object_id = ddios.object_id
WHERE   ddios.page_lock_wait_in_ms > 0
ORDER BY ddios.page_lock_wait_count DESC;
--丢失索引
SELECT  user_seeks * avg_total_user_cost * ( avg_user_impact * 0.01 ) AS [index_advantage] ,
        dbmigs.last_user_seek ,
        dbmid.[statement] AS [Database.Schema.Table] ,
        dbmid.equality_columns ,
        dbmid.inequality_columns ,
        dbmid.included_columns ,
        dbmigs.unique_compiles ,
        dbmigs.user_seeks ,
        dbmigs.avg_total_user_cost ,
        dbmigs.avg_user_impact
FROM    sys.dm_db_missing_index_group_stats AS dbmigs WITH ( NOLOCK )
        INNER JOIN sys.dm_db_missing_index_groups AS dbmig WITH ( NOLOCK ) ON dbmigs.group_handle = dbmig.index_group_handle
        INNER JOIN sys.dm_db_missing_index_details AS dbmid WITH ( NOLOCK ) ON dbmig.index_handle = dbmid.index_handle
WHERE   dbmid.[database_id] = DB_ID()
ORDER BY index_advantage DESC;
--索引上的碎片超过15%并且索引体积较大（超过500页）的索引。
SELECT  '[' + DB_NAME() + '].[' + OBJECT_SCHEMA_NAME(ddips.[object_id],
                                                     DB_ID()) + '].['
        + OBJECT_NAME(ddips.[object_id], DB_ID()) + ']' AS [statement] ,
        i.[name] AS [index_name] ,
        ddips.[index_type_desc] ,
        ddips.[partition_number] ,
        ddips.[alloc_unit_type_desc] ,
        ddips.[index_depth] ,
        ddips.[index_level] ,
        CAST(ddips.[avg_fragmentation_in_percent] AS SMALLINT) AS [avg_frag_%] ,
        CAST(ddips.[avg_fragment_size_in_pages] AS SMALLINT) AS [avg_frag_size_in_pages] ,
        ddips.[fragment_count] ,
        ddips.[page_count]
FROM    sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'limited') ddips
        INNER JOIN sys.[indexes] i ON ddips.[object_id] = i.[object_id]
                                      AND ddips.[index_id] = i.[index_id]
WHERE   ddips.[avg_fragmentation_in_percent] > 15
        AND ddips.[page_count] > 500
ORDER BY ddips.[avg_fragmentation_in_percent] ,
        OBJECT_NAME(ddips.[object_id], DB_ID()) ,
        i.[name]

锁定篇

--查看因为单条UPDATE语句锁住的用户表
SELECT  [resource_type] ,
        DB_NAME([resource_database_id]) AS [Database Name] ,
        CASE WHEN DTL.resource_type IN ( 'DATABASE', 'FILE', 'METADATA' )
             THEN DTL.resource_type
             WHEN DTL.resource_type = 'OBJECT'
             THEN OBJECT_NAME(DTL.resource_associated_entity_id,
                              DTL.[resource_database_id])
             WHEN DTL.resource_type IN ( 'KEY', 'PAGE', 'RID' )
             THEN ( SELECT  OBJECT_NAME([object_id])
                    FROM    sys.partitions
                    WHERE   sys.partitions.hobt_id = DTL.resource_associated_entity_id
                  )
             ELSE 'Unidentified'
        END AS requested_object_name ,
        [request_mode] ,
        [resource_description]
FROM    sys.dm_tran_locks DTL
WHERE   DTL.[resource_type] <> 'DATABASE';


--哪个会话引起阻塞并且它们在运行什么
SELECT  DTL.[request_session_id] AS [session_id] ,
        DB_NAME(DTL.[resource_database_id]) AS [Database] ,
        DTL.resource_type ,
        CASE WHEN DTL.resource_type IN ( 'DATABASE', 'FILE', 'METADATA' )
             THEN DTL.resource_type
             WHEN DTL.resource_type = 'OBJECT'
             THEN OBJECT_NAME(DTL.resource_associated_entity_id,
                              DTL.[resource_database_id])
             WHEN DTL.resource_type IN ( 'KEY', 'PAGE', 'RID' )
             THEN ( SELECT  OBJECT_NAME([object_id])
                    FROM    sys.partitions
                    WHERE   sys.partitions.hobt_id = DTL.resource_associated_entity_id
                  )
             ELSE 'Unidentified'
        END AS [Parent Object] ,
        DTL.request_mode AS [Lock Type] ,
        DTL.request_status AS [Request Status] ,
        DER.[blocking_session_id] ,
        DES.[login_name] ,
        CASE DTL.request_lifetime
          WHEN 0 THEN DEST_R.TEXT
          ELSE DEST_C.TEXT
        END AS [Statement]
FROM    sys.dm_tran_locks DTL
        LEFT JOIN sys.[dm_exec_requests] DER ON DTL.[request_session_id] = DER.[session_id]
        INNER JOIN sys.dm_exec_sessions DES ON DTL.request_session_id = DES.[session_id]
        INNER JOIN sys.dm_exec_connections DEC ON DTL.[request_session_id] = DEC.[most_recent_session_id]
        OUTER APPLY sys.dm_exec_sql_text(DEC.[most_recent_sql_handle]) AS DEST_C
        OUTER APPLY sys.dm_exec_sql_text(DER.sql_handle) AS DEST_R
WHERE   DTL.[resource_database_id] = DB_ID()
        AND DTL.[resource_type] NOT IN ( 'DATABASE', 'METADATA' )
ORDER BY DTL.[request_session_id];

--单库中的锁定和阻塞
SELECT  DTL.[resource_type] AS [resource type] ,
        CASE WHEN DTL.[resource_type] IN ( 'DATABASE', 'FILE', 'METADATA' )
             THEN DTL.[resource_type]
             WHEN DTL.[resource_type] = 'OBJECT'
             THEN OBJECT_NAME(DTL.resource_associated_entity_id)
             WHEN DTL.[resource_type] IN ( 'KEY', 'PAGE', 'RID' )
             THEN ( SELECT  OBJECT_NAME([object_id])
                    FROM    sys.partitions
                    WHERE   sys.partitions.[hobt_id] = DTL.[resource_associated_entity_id]
                  )
             ELSE 'Unidentified'
        END AS [Parent Object] ,
        DTL.[request_mode] AS [Lock Type] ,
        DTL.[request_status] AS [Request Status] ,
        DOWT.[wait_duration_ms] AS [wait duration ms] ,
        DOWT.[wait_type] AS [wait type] ,
        DOWT.[session_id] AS [blocked session id] ,
        DES_blocked.[login_name] AS [blocked_user] ,
        SUBSTRING(dest_blocked.text, der.statement_start_offset / 2,
                  ( CASE WHEN der.statement_end_offset = -1
                         THEN DATALENGTH(dest_blocked.text)
                         ELSE der.statement_end_offset
                    END - der.statement_start_offset ) / 2) AS [blocked_command] ,
        DOWT.[blocking_session_id] AS [blocking session id] ,
        DES_blocking.[login_name] AS [blocking user] ,
        DEST_blocking.[text] AS [blocking command] ,
        DOWT.resource_description AS [blocking resource detail]
FROM    sys.dm_tran_locks DTL
        INNER JOIN sys.dm_os_waiting_tasks DOWT ON DTL.lock_owner_address = DOWT.resource_address
        INNER JOIN sys.[dm_exec_requests] DER ON DOWT.[session_id] = DER.[session_id]
        INNER JOIN sys.dm_exec_sessions DES_blocked ON DOWT.[session_id] = DES_Blocked.[session_id]
        INNER JOIN sys.dm_exec_sessions DES_blocking ON DOWT.[blocking_session_id] = DES_Blocking.[session_id]
        INNER JOIN sys.dm_exec_connections DEC ON DTL.[request_session_id] = DEC.[most_recent_session_id]
        CROSS APPLY sys.dm_exec_sql_text(DEC.[most_recent_sql_handle]) AS DEST_Blocking
        CROSS APPLY sys.dm_exec_sql_text(DER.sql_handle) AS DEST_Blocked
WHERE   DTL.[resource_database_id] = DB_ID()

使用 Profiler 获取性能数据

从sQL Server 2000开始Profiler就存在，当时称为事件探查器，但是从SQL Server2005开始才称为Profiler。它是一个捕获和分析事件的强大工具，得到的结果集可以用于很多性能问题和运行问题的侦测。

DBCC命令

DBCC命令原本是供微软内部使用的，但是后来逐步放开了。不过有些很重要的功能
依旧没有公开。这里重点演示几个常用的 DBCC命令:
DBCC sQLPERF
DBCC INPUTBUFFER
DBCC TRACEON/TRACEOFF
DBCC SHOWCONTIG
DBCC OPENTRAN

查着数据库的日志使用情况

很多人会遇到SQL Server中某个库的日志量暴增的情况，却不知道是什么原因，于是
便选择使用暴力的方法解决，如分离→删除LDF 文件→附件，让SQL Server重新生成LDF
文件。这种方法相当不可取，因为LDF包含了非常重要的信息，如果就这样删除了，轻则
丢失一些未提交的数据，重则数据库无法使用。对于这种问题，可以先到sys.databases中
查看log_reuse_desc字段的信息。一般来说，出现这种情况都是因为没有管理好数据库导致
的，可以用如下命令来查看数据库的使用情况:

USE master
go
--创建测试库
IF DB_ID('Log_Demo') IS NOT NULL
    DROP DATABASE Log_Demo
go
CREATE DATABASE Log_Demo
go
ALTER DATABASE Log_Demo SET RECOVERY FULL 
go 
USE Log_Demo
go
--创建测试表
IF OBJECT_ID('Table_demo', 'U') IS NOT NULL
    DROP TABLE Table_demo
go
CREATE TABLE Table_demo
    (
      id INT IDENTITY(1, 1) ,
      name CHAR(8000)
    )
go
--检查日志使用情况
DBCC sqlperf(logspace)
go
--插入10000条数据
INSERT  INTO Table_demo
        ( name )
VALUES  ( 'test' )
go 10000
--再次检查日志情况
DBCC sqlperf(logspace)
go

可以看到，Log Size没有变小，但是Log Space Used已经降低。可见，通过这个命令，可以检查日志的使用情况，并决定是否需要进行日志备份以控制日志文件的大小。