Performance Tuning with SQL Server Dynamic Management Views

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Chapter 5: Indexing Strategy and Maintenance AND database_id = DB_ID() ) AND o.[type] = 'U' ORDER BY OBJECT_NAME(i.[object_id]) ASC ; Listing 5.4: Finding unused indexes. If <strong>SQL</strong> <strong>Server</strong> has been running long enough for you to have a complete, representative workload, there is a good chance that those indexes (and perhaps tables) are "dead," meaning they are no longer used by your database and can potentially be dropped, after some further investigation. Identify indexes that are being maintained but not used Listing 5.5 identifies clustered and non-clustered indexes that are consuming resources, in terms of writes and maintenance, but are never being selected for use by the optimizer, so have never been read, at least since the last time the cache was cleared of accumulated usage data. It uses a fully-qualified naming convention and is identified as "statement," in order to conform to the output that you will see when querying the missing indexes DMOs. We identify the name of the index via a join to the sys.indexes system catalog view, on the object_id and index_id columns, and we join to the sys.partitions system view on the same columns in order to return the total_rows metric (the total number of rows in the index). 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] 186
Chapter 5: Indexing Strategy and Maintenance 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 ] Listing 5.5: Querying sys.dm_db_index_usage_stats for indexes that are being maintained but not used. 187
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High Performance SQL Server Perform
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Copyright Louis Davidson and Tim Fo
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Dissecting user activity ..........
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Getting Stats about tempdb Usage ..
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Server (PASS) since 2002. He has al
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Tim Ford I dedicate this book to Am
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13 Introduction on those objects th
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Code Examples 15 Introduction Throu
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Chapter 1: Using Dynamic Management
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DMO Security and Permissions Chapte
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We can find out, for example: Chapt
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Beware of the watcher effect Chapte
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Chapter 2: Connections, Sessions an
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Sysprocesses versus DMOs Chapter 2:
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Listing 2.3: Who is connected? Chap
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Listing 2.4: Who is executing what
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Logins with more than one session C
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DECLARE @days_old SMALLINT SELECT @
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• dbcc shrinkdatabase / shrinkfil
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This will return (with a different
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Who is running what, right now? Cha
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Summary Chapter 2: Connections, Ses
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73 Chapter 3: Query Plan Metadata P
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75 Chapter 3: Query Plan Metadata P
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77 Chapter 3: Query Plan Metadata t
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79 Chapter 3: Query Plan Metadata U
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SELECT TOP 10 object_id , name FROM
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Dissecting the SQL text 83 Chapter
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Figure 3.2: Three queries returned
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87 Chapter 3: Query Plan Metadata T
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89 Chapter 3: Query Plan Metadata
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Criteria in determing plan reuse 91
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For a server that had been up for t
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Listing 3.9: Investigating the most
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SELECT FirstName , LastName FROM db
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99 Chapter 3: Query Plan Metadata C
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Listing 3.14: Finding the CPU-inten
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WHERE execText.text like '%account%
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115 Chapter 4: Transactions We'll a
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117 Chapter 4: Transactions unique
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Snapshot isolation level 119 Chapte
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121 Chapter 4: Transactions • res
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Lock types 123 Chapter 4: Transacti
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127 Chapter 4: Transactions SELECT
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129 Chapter 4: Transactions If, fro
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133 Chapter 4: Transactions When in
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Page 189 and 190: Identify inefficient indexes Chapte
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CREATE TABLE testHeap ( testHeapId
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Chapter 6: Physical Disk Statistics
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Viewing pending I/O requests Chapte
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Amount of data read versus written
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The results are as follows: Chapter
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Finding the most common waits 267 C
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WHERE cntr_type = @PERF_COUNTER_LAR
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DECLARE @PERF_LARGE_RAW_FRACTION IN
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ORDER BY dopc_fraction.object_name
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) time DATETIME DEFAULT ( GETDATE()
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DECLARE @PERF_AVERAGE_BULK INT , @P
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• cpu_count - number of logical p
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The max worker threads option. 293
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• work_queue_count - number of ta
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WHERE scheduler_id < 255 AND runnab
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System-wide memory use 303 Chapter
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As stated by Books Online: 307 Chap
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• name - the descriptive name giv
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Summary 319 Chapter 7: OS and Hardw
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Index A ACID test 116 Activity and
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P Performance counters 277-291 aver
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sys.dm_tran_database_transactions 1
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SQL Compare ® Pro Compare and sync
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Deployment Manager Automated deploy
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SQL Monitor from $795 SQL Server pe
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You can buy our acclaimed SQL Serve
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.NET Reflector Decompile, debug, an
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The Red Gate Guides SQL Server Back
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Performance Tuning with SQL Server Dynamic Management Views

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