Summit 2010 Abstract Submission

Jeremiah Peschka just tweeted about the looming deadline to submit an abstract for Summit 2010. I’ve been trying to think of a good topic to present on, and this finally got my butt in gear to submit one! For those interested, here’s what I submitted:

Heaps of Trouble, Clusters of Glory – A Look At Index Internals

Indexes are a crucial component of SQL Server, especially in performance tuning, yet many DBA’s don’t fully understand how indexes work. In this in-depth session, Michelle will examine the anatomy of indexes, from how they’re stored to how they get fragmented. And to make our inner geeks happy, she’ll look at page data to show you what’s happening behind the scenes. Topics covered will include index structure, fragmentation and defragmentation, index partitioning, and index filtering. If you’ve ever wondered just *what* goes on in an index, don’t miss this session!

Special thanks to Chris for help with the session title. :)

Index Defrag Script, v4.0

UPDATE: This script has been updated. Please view the latest version at http://sqlfool.com/2011/06/index-defrag-script-v4-1/.

In my blog post, “Index Defrag Script Updates – Beta Testers Needed“, I stated “I’ll hopefully have the new version online in just a few days.” That was dated January 26th. I had every intention of following through with it, too, but something came up:

My daughter, Chloe Lynn, was born on February 10th. She’s a happy, healthy baby girl who consumes all of my free time and already has both her parents wrapped around her adorable little finger. So while I apologize for the delay in posting the latest version, I hope you can understand and forgive me. :)

Alrighty, back to SQL stuff! This version of the script has been significantly overhauled from previous versions. Here’s a full synopsis of the changes and enhancements:

- There’s now a time limit option so you have more control over how long your defrags run. This time limit is checked *before* a defrag is begun, so it’s still possible to have a defrag occur after the time limit is exceeded (i.e. a large index).

- I’ve added a static table for managing the index defrag scans. This way, you can start and stop the defrag process without the need to rescan. This is especially useful for VLDB’s or any environment where you’re unable to complete the defrags in one operation.

- Just in case you want to perform a rescan, even if there’s still indexes left to defrag from your last rescan, there’s a parameter to force it.

- There’s now an option to sort by page count, range scan count, or fragmentation level. Range scan count is defaulted, as the indexes that have high amounts of range scans will benefit the most from having a defragged index. You can also specify whether you want to sort by ASC or DESC.

- There’s now min and max parameters for page counts. This is useful for a) ignoring indexes with less than 1 extent (as recommended by Microsoft) and b) for scheduling index operations by size. For instance, you may want to defrag your small indexes during business hours but leave your big indexes for evening or weekend hours.

- There’s now a parameterized option for sorting in TEMPDB. This may reduce execution time and will prevent unnecessary database file size inflation during defrags. NOTE: Make sure you have enough free space in TEMPDB prior to enabling this option.

- I moved the SQL statement output to display before execution so you can see what’s currently executing.

- I’ve added a debug output of the parameters selected. I’ve added additional validation to the start of the script, so this will help show you if an invalid value was submitted and overwritten.

- I’ve added new columns to the log table to show what command is being executed and what error, if any, occurred when trying to execute.

- I’ve added try/catch logic to handle errors during execution; this way, a single error will not prevent the whole script from terminating.

- The script will now force a rebuild for indexes with allow_page_locks = off.

- For those who use partitioning, you can now exclude the right-most populated partition from the defrag operation. This won’t be applicable for all partitioning schemes, but for sliding-window scenarios (one of the most common schemes), it’ll reduce contention on the partition that’s being actively written to.

- I’ve fixed a bug where tables with LOB indexes may have more than one record returned from sys.dm_db_index_physical_stats.

- For various reasons, I’ve removed the option to rebuild stats.

Also, if you have a previous version of the script installed, this version will rename those tables, since there have been some changes made to them.

FAQ:

I often receive the same questions about this script, so allow me to answer them here:

“I keep running the script, but my index is still fragmented. Why?”
This is most likely a very small index. Here’s what Microsoft has to say:

“In general, fragmentation on small indexes is often not controllable. The pages of small indexes are stored on mixed extents. Mixed extents are shared by up to eight objects, so the fragmentation in a small index might not be reduced after reorganizing or rebuilding the index. For more information about mixed extents, see Understanding Pages and Extents.”

“What database should I create it in?” or “Can I create this in the MASTER database?”
It’s up to you where you create it. You could technically create it in the MASTER database, but I recommend creating a utility database for your DBA administrative tasks.

“Can I run this againt a SharePoint database?”
I’ve never tried personally, but I’ve been told it runs just fine.

“What are the minimum requirements to run this script?” or “Will this run on SQL Server 2000 instances?”
You need to be on SQL Server 2005 SP2 or higher.

Without further ado, here’s the script:

UPDATE: This script has been updated. Please view the latest version at http://sqlfool.com/2011/06/index-defrag-script-v4-1/.

/* Scroll down to the see notes, disclaimers, and licensing information */
 
Declare @indexDefragLog_rename      varchar(128)
    , @indexDefragExclusion_rename  varchar(128)
    , @indexDefragStatus_rename     varchar(128);
 
Select @indexDefragLog_rename       = 'dba_indexDefragLog_obsolete_' + Convert(varchar(10), GetDate(), 112)
    , @indexDefragExclusion_rename  = 'dba_indexDefragExclusion_obsolete_' + Convert(varchar(10), GetDate(), 112)
    , @indexDefragStatus_rename     = 'dba_indexDefragStatus_obsolete_' + Convert(varchar(10), GetDate(), 112);
 
If Exists(Select [object_id] From sys.tables Where [name] = 'dba_indexDefragLog')
    Execute sp_rename dba_indexDefragLog, @indexDefragLog_rename;
 
If Exists(Select [object_id] From sys.tables Where [name] = 'dba_indexDefragExclusion')
    Execute sp_rename dba_indexDefragExclusion, @indexDefragExclusion_rename;
 
If Exists(Select [object_id] From sys.tables Where [name] = 'dba_indexDefragStatus')
    Execute sp_rename dba_indexDefragStatus, @indexDefragStatus_rename;
Go
 
Create Table dbo.dba_indexDefragLog
(
      indexDefrag_id    int identity(1,1)   Not Null
    , databaseID        int                 Not Null
    , databaseName      nvarchar(128)       Not Null
    , objectID          int                 Not Null
    , objectName        nvarchar(128)       Not Null
    , indexID           int                 Not Null
    , indexName         nvarchar(128)       Not Null
    , partitionNumber   smallint            Not Null
    , fragmentation     float               Not Null
    , page_count        int                 Not Null
    , dateTimeStart     datetime            Not Null
    , dateTimeEnd       datetime            Null
    , durationSeconds   int                 Null
    , sqlStatement      varchar(4000)       Null
    , errorMessage      varchar(1000)       Null
 
    Constraint PK_indexDefragLog_v40
        Primary Key Clustered (indexDefrag_id)
);
 
Print 'dba_indexDefragLog Table Created';
 
Create Table dbo.dba_indexDefragExclusion
(
      databaseID        int                 Not Null
    , databaseName      nvarchar(128)       Not Null
    , objectID          int                 Not Null
    , objectName        nvarchar(128)       Not Null
    , indexID           int                 Not Null
    , indexName         nvarchar(128)       Not Null
    , exclusionMask     int                 Not Null
        /* 1=Sunday, 2=Monday, 4=Tuesday, 8=Wednesday, 16=Thursday, 32=Friday, 64=Saturday */
 
    Constraint PK_indexDefragExclusion_v40
        Primary Key Clustered (databaseID, objectID, indexID)
);
 
Print 'dba_indexDefragExclusion Table Created';
 
Create Table dbo.dba_indexDefragStatus
(
      databaseID        int
    , databaseName      nvarchar(128)
    , objectID          int
    , indexID           int
    , partitionNumber   smallint
    , fragmentation     float
    , page_count        int
    , range_scan_count  bigint
    , schemaName        nvarchar(128)   Null
    , objectName        nvarchar(128)   Null
    , indexName         nvarchar(128)   Null
    , scanDate          datetime        
    , defragDate        datetime        Null
    , printStatus       bit             Default(0)
    , exclusionMask     int             Default(0)
 
    Constraint PK_indexDefragStatus_v40
        Primary Key Clustered(databaseID, objectID, indexID, partitionNumber)
);
 
Print 'dba_indexDefragStatus Table Created';
 
If ObjectProperty(Object_ID('dbo.dba_indexDefrag_sp'), N'IsProcedure') = 1
Begin
    Drop Procedure dbo.dba_indexDefrag_sp;
    Print 'Procedure dba_indexDefrag_sp dropped';
End;
Go
 
Create Procedure dbo.dba_indexDefrag_sp
 
    /* Declare Parameters */
      @minFragmentation     float           = 10.0  
        /* in percent, will not defrag if fragmentation less than specified */
    , @rebuildThreshold     float           = 30.0  
        /* in percent, greater than @rebuildThreshold will result in rebuild instead of reorg */
    , @executeSQL           bit             = 1     
        /* 1 = execute; 0 = print command only */
    , @defragOrderColumn    nvarchar(20)    = 'range_scan_count'
        /* Valid options are: range_scan_count, fragmentation, page_count */
    , @defragSortOrder      nvarchar(4)     = 'DESC'
        /* Valid options are: ASC, DESC */
    , @timeLimit            int             = 720 /* defaulted to 12 hours */
        /* Optional time limitation; expressed in minutes */
    , @database             varchar(128)    = Null
        /* Option to specify a database name; null will return all */
    , @tableName            varchar(4000)   = Null  -- databaseName.schema.tableName
        /* Option to specify a table name; null will return all */
    , @forceRescan          bit             = 0
        /* Whether or not to force a rescan of indexes; 1 = force, 0 = use existing scan, if available */
    , @scanMode             varchar(10)     = N'LIMITED'
        /* Options are LIMITED, SAMPLED, and DETAILED */
    , @minPageCount         int             = 8 
        /*  MS recommends > 1 extent (8 pages) */
    , @maxPageCount         int             = Null
        /* NULL = no limit */
    , @excludeMaxPartition  bit             = 0
        /* 1 = exclude right-most populated partition; 0 = do not exclude; see notes for caveats */
    , @onlineRebuild        bit             = 1     
        /* 1 = online rebuild; 0 = offline rebuild; only in Enterprise */
    , @sortInTempDB         bit             = 1
        /* 1 = perform sort operation in TempDB; 0 = perform sort operation in the index's database */
    , @maxDopRestriction    tinyint         = Null
        /* Option to restrict the number of processors for the operation; only in Enterprise */
    , @printCommands        bit             = 0     
        /* 1 = print commands; 0 = do not print commands */
    , @printFragmentation   bit             = 0
        /* 1 = print fragmentation prior to defrag; 
           0 = do not print */
    , @defragDelay          char(8)         = '00:00:05'
        /* time to wait between defrag commands */
    , @debugMode            bit             = 0
        /* display some useful comments to help determine if/where issues occur */
 
As
/*********************************************************************************
    Name:       dba_indexDefrag_sp
 
    Author:     Michelle Ufford, http://sqlfool.com
 
    Purpose:    Defrags one or more indexes for one or more databases
 
    Notes:
 
    CAUTION: TRANSACTION LOG SIZE SHOULD BE MONITORED CLOSELY WHEN DEFRAGMENTING.
             DO NOT RUN UNATTENDED ON LARGE DATABASES DURING BUSINESS HOURS.
 
      @minFragmentation     defaulted to 10%, will not defrag if fragmentation 
                            is less than that
 
      @rebuildThreshold     defaulted to 30% as recommended by Microsoft in BOL;
                            greater than 30% will result in rebuild instead
 
      @executeSQL           1 = execute the SQL generated by this proc; 
                            0 = print command only
 
      @defragOrderColumn    Defines how to prioritize the order of defrags.  Only
                            used if @executeSQL = 1.  
                            Valid options are: 
                            range_scan_count = count of range and table scans on the
                                               index; in general, this is what benefits 
                                               the most from defragmentation
                            fragmentation    = amount of fragmentation in the index;
                                               the higher the number, the worse it is
                            page_count       = number of pages in the index; affects
                                               how long it takes to defrag an index
 
      @defragSortOrder      The sort order of the ORDER BY clause.
                            Valid options are ASC (ascending) or DESC (descending).
 
      @timeLimit            Optional, limits how much time can be spent performing 
                            index defrags; expressed in minutes.
 
                            NOTE: The time limit is checked BEFORE an index defrag
                                  is begun, thus a long index defrag can exceed the
                                  time limitation.
 
      @database             Optional, specify specific database name to defrag;
                            If not specified, all non-system databases will
                            be defragged.
 
      @tableName            Specify if you only want to defrag indexes for a 
                            specific table, format = databaseName.schema.tableName;
                            if not specified, all tables will be defragged.
 
      @forceRescan          Whether or not to force a rescan of indexes.  If set
                            to 0, a rescan will not occur until all indexes have
                            been defragged.  This can span multiple executions.
                            1 = force a rescan
                            0 = use previous scan, if there are indexes left to defrag
 
      @scanMode             Specifies which scan mode to use to determine
                            fragmentation levels.  Options are:
                            LIMITED - scans the parent level; quickest mode,
                                      recommended for most cases.
                            SAMPLED - samples 1% of all data pages; if less than
                                      10k pages, performs a DETAILED scan.
                            DETAILED - scans all data pages.  Use great care with
                                       this mode, as it can cause performance issues.
 
      @minPageCount         Specifies how many pages must exist in an index in order 
                            to be considered for a defrag.  Defaulted to 8 pages, as 
                            Microsoft recommends only defragging indexes with more 
                            than 1 extent (8 pages).  
 
                            NOTE: The @minPageCount will restrict the indexes that
                            are stored in dba_indexDefragStatus table.
 
      @maxPageCount         Specifies the maximum number of pages that can exist in 
                            an index and still be considered for a defrag.  Useful
                            for scheduling small indexes during business hours and
                            large indexes for non-business hours.
 
                            NOTE: The @maxPageCount will restrict the indexes that
                            are defragged during the current operation; it will not
                            prevent indexes from being stored in the 
                            dba_indexDefragStatus table.  This way, a single scan
                            can support multiple page count thresholds.
 
      @excludeMaxPartition  If an index is partitioned, this option specifies whether
                            to exclude the right-most populated partition.  Typically,
                            this is the partition that is currently being written to in
                            a sliding-window scenario.  Enabling this feature may reduce
                            contention.  This may not be applicable in other types of 
                            partitioning scenarios.  Non-partitioned indexes are 
                            unaffected by this option.
                            1 = exclude right-most populated partition
                            0 = do not exclude
 
      @onlineRebuild        1 = online rebuild; 
                            0 = offline rebuild
 
      @sortInTempDB         Specifies whether to defrag the index in TEMPDB or in the
                            database the index belongs to.  Enabling this option may
                            result in faster defrags and prevent database file size 
                            inflation.
                            1 = perform sort operation in TempDB
                            0 = perform sort operation in the index's database 
 
      @maxDopRestriction    Option to specify a processor limit for index rebuilds
 
      @printCommands        1 = print commands to screen; 
                            0 = do not print commands
 
      @printFragmentation   1 = print fragmentation to screen;
                            0 = do not print fragmentation
 
      @defragDelay          Time to wait between defrag commands; gives the
                            server a little time to catch up 
 
      @debugMode            1 = display debug comments; helps with troubleshooting
                            0 = do not display debug comments
 
    Called by:  SQL Agent Job or DBA
 
    ----------------------------------------------------------------------------
    DISCLAIMER: 
    This code and information are provided "AS IS" without warranty of any kind,
    either expressed or implied, including but not limited to the implied 
    warranties or merchantability and/or fitness for a particular purpose.
    ----------------------------------------------------------------------------
    LICENSE: 
    This index defrag script is free to download and use for personal, educational, 
    and internal corporate purposes, provided that this header is preserved. 
    Redistribution or sale of this index defrag script, in whole or in part, is 
    prohibited without the author's express written consent.
    ----------------------------------------------------------------------------
    Date        Initials	Version Description
    ----------------------------------------------------------------------------
    2007-12-18  MFU         1.0     Initial Release
    2008-10-17  MFU         1.1     Added @defragDelay, CIX_temp_indexDefragList
    2008-11-17  MFU         1.2     Added page_count to log table
                                    , added @printFragmentation option
    2009-03-17  MFU         2.0     Provided support for centralized execution
                                    , consolidated Enterprise & Standard versions
                                    , added @debugMode, @maxDopRestriction
                                    , modified LOB and partition logic  
    2009-06-18  MFU         3.0     Fixed bug in LOB logic, added @scanMode option
                                    , added support for stat rebuilds (@rebuildStats)
                                    , support model and msdb defrag
                                    , added columns to the dba_indexDefragLog table
                                    , modified logging to show "in progress" defrags
                                    , added defrag exclusion list (scheduling)
    2009-08-28  MFU         3.1     Fixed read_only bug for database lists
    2010-04-20  MFU         4.0     Added time limit option
                                    , added static table with rescan logic
                                    , added parameters for page count & SORT_IN_TEMPDB
                                    , added try/catch logic and additional debug options
                                    , added options for defrag prioritization
                                    , fixed bug for indexes with allow_page_lock = off
                                    , added option to exclude right-most partition
                                    , removed @rebuildStats option
                                    , refer to http://sqlfool.com for full release notes
*********************************************************************************
    Example of how to call this script:
 
        Exec dbo.dba_indexDefrag_sp
              @executeSQL           = 1
            , @printCommands        = 1
            , @debugMode            = 1
            , @printFragmentation   = 1
            , @forceRescan          = 1
            , @maxDopRestriction    = 1
            , @minPageCount         = 8
            , @maxPageCount         = Null
            , @minFragmentation     = 1
            , @rebuildThreshold     = 30
            , @defragDelay          = '00:00:05'
            , @defragOrderColumn    = 'page_count'
            , @defragSortOrder      = 'DESC'
            , @excludeMaxPartition  = 1
            , @timeLimit            = Null;
*********************************************************************************/																
Set NoCount On;
Set XACT_Abort On;
Set Quoted_Identifier On;
 
Begin
 
    Begin Try
 
        /* Just a little validation... */
        If @minFragmentation Is Null 
            Or @minFragmentation Not Between 0.00 And 100.0
                Set @minFragmentation = 10.0;
 
        If @rebuildThreshold Is Null
            Or @rebuildThreshold Not Between 0.00 And 100.0
                Set @rebuildThreshold = 30.0;
 
        If @defragDelay Not Like '00:[0-5][0-9]:[0-5][0-9]'
            Set @defragDelay = '00:00:05';
 
        If @defragOrderColumn Is Null
            Or @defragOrderColumn Not In ('range_scan_count', 'fragmentation', 'page_count')
                Set @defragOrderColumn = 'range_scan_count';
 
        If @defragSortOrder Is Null
            Or @defragSortOrder Not In ('ASC', 'DESC')
                Set @defragSortOrder = 'DESC';
 
        If @scanMode Not In ('LIMITED', 'SAMPLED', 'DETAILED')
            Set @scanMode = 'LIMITED';
 
        If @debugMode Is Null
            Set @debugMode = 0;
 
        If @forceRescan Is Null
            Set @forceRescan = 0;
 
        If @sortInTempDB Is Null
            Set @sortInTempDB = 1;
 
 
        If @debugMode = 1 RaisError('Undusting the cogs and starting up...', 0, 42) With NoWait;
 
        /* Declare our variables */
        Declare   @objectID                 int
                , @databaseID               int
                , @databaseName             nvarchar(128)
                , @indexID                  int
                , @partitionCount           bigint
                , @schemaName               nvarchar(128)
                , @objectName               nvarchar(128)
                , @indexName                nvarchar(128)
                , @partitionNumber          smallint
                , @fragmentation            float
                , @pageCount                int
                , @sqlCommand               nvarchar(4000)
                , @rebuildCommand           nvarchar(200)
                , @dateTimeStart            datetime
                , @dateTimeEnd              datetime
                , @containsLOB              bit
                , @editionCheck             bit
                , @debugMessage             nvarchar(4000)
                , @updateSQL                nvarchar(4000)
                , @partitionSQL             nvarchar(4000)
                , @partitionSQL_Param       nvarchar(1000)
                , @LOB_SQL                  nvarchar(4000)
                , @LOB_SQL_Param            nvarchar(1000)
                , @indexDefrag_id           int
                , @startDateTime            datetime
                , @endDateTime              datetime
                , @getIndexSQL              nvarchar(4000)
                , @getIndexSQL_Param        nvarchar(4000)
                , @allowPageLockSQL         nvarchar(4000)
                , @allowPageLockSQL_Param   nvarchar(4000)
                , @allowPageLocks           int
                , @excludeMaxPartitionSQL   nvarchar(4000);
 
        /* Initialize our variables */
        Select @startDateTime = GetDate()
            , @endDateTime = DateAdd(minute, @timeLimit, GetDate());
 
        /* Create our temporary tables */
        Create Table #databaseList
        (
              databaseID        int
            , databaseName      varchar(128)
            , scanStatus        bit
        );
 
        Create Table #processor 
        (
              [index]           int
            , Name              varchar(128)
            , Internal_Value    int
            , Character_Value   int
        );
 
        Create Table #maxPartitionList
        (
              databaseID        int
            , objectID          int
            , indexID           int
            , maxPartition      int
        );
 
        If @debugMode = 1 RaisError('Beginning validation...', 0, 42) With NoWait;
 
        /* Make sure we're not exceeding the number of processors we have available */
        Insert Into #processor
        Execute xp_msver 'ProcessorCount';
 
        If @maxDopRestriction Is Not Null And @maxDopRestriction > (Select Internal_Value From #processor)
            Select @maxDopRestriction = Internal_Value
            From #processor;
 
        /* Check our server version; 1804890536 = Enterprise, 610778273 = Enterprise Evaluation, -2117995310 = Developer */
        If (Select ServerProperty('EditionID')) In (1804890536, 610778273, -2117995310) 
            Set @editionCheck = 1 -- supports online rebuilds
        Else
            Set @editionCheck = 0; -- does not support online rebuilds
 
        /* Output the parameters we're working with */
        If @debugMode = 1 
        Begin
 
            Select @debugMessage = 'Your selected parameters are... 
            Defrag indexes with fragmentation greater than ' + Cast(@minFragmentation As varchar(10)) + ';
            Rebuild indexes with fragmentation greater than ' + Cast(@rebuildThreshold As varchar(10)) + ';
            You' + Case When @executeSQL = 1 Then ' DO' Else ' DO NOT' End + ' want the commands to be executed automatically; 
            You want to defrag indexes in ' + @defragSortOrder + ' order of the ' + UPPER(@defragOrderColumn) + ' value;
            You have' + Case When @timeLimit Is Null Then ' not specified a time limit;' Else ' specified a time limit of ' 
                + Cast(@timeLimit As varchar(10)) End + ' minutes;
            ' + Case When @database Is Null Then 'ALL databases' Else 'The ' + @database + ' database' End + ' will be defragged;
            ' + Case When @tableName Is Null Then 'ALL tables' Else 'The ' + @tableName + ' table' End + ' will be defragged;
            We' + Case When Exists(Select Top 1 * From dbo.dba_indexDefragStatus Where defragDate Is Null)
                And @forceRescan <> 1 Then ' WILL NOT' Else ' WILL' End + ' be rescanning indexes;
            The scan will be performed in ' + @scanMode + ' mode;
            You want to limit defrags to indexes with' + Case When @maxPageCount Is Null Then ' more than ' 
                + Cast(@minPageCount As varchar(10)) Else
                ' between ' + Cast(@minPageCount As varchar(10))
                + ' and ' + Cast(@maxPageCount As varchar(10)) End + ' pages;
            Indexes will be defragged' + Case When @editionCheck = 0 Or @onlineRebuild = 0 Then ' OFFLINE;' Else ' ONLINE;' End + '
            Indexes will be sorted in' + Case When @sortInTempDB = 0 Then ' the DATABASE' Else ' TEMPDB;' End + '
            Defrag operations will utilize ' + Case When @editionCheck = 0 Or @maxDopRestriction Is Null 
                Then 'system defaults for processors;' 
                Else Cast(@maxDopRestriction As varchar(2)) + ' processors;' End + '
            You' + Case When @printCommands = 1 Then ' DO' Else ' DO NOT' End + ' want to print the ALTER INDEX commands; 
            You' + Case When @printFragmentation = 1 Then ' DO' Else ' DO NOT' End + ' want to output fragmentation levels; 
            You want to wait ' + @defragDelay + ' (hh:mm:ss) between defragging indexes;
            You want to run in' + Case When @debugMode = 1 Then ' DEBUG' Else ' SILENT' End + ' mode.';
 
            RaisError(@debugMessage, 0, 42) With NoWait;
 
        End;
 
        If @debugMode = 1 RaisError('Grabbing a list of our databases...', 0, 42) With NoWait;
 
        /* Retrieve the list of databases to investigate */
        Insert Into #databaseList
        Select database_id
            , name
            , 0 -- not scanned yet for fragmentation
        From sys.databases
        Where name = IsNull(@database, name)
            And [name] Not In ('master', 'tempdb')-- exclude system databases
            And [state] = 0 -- state must be ONLINE
            And is_read_only = 0;  -- cannot be read_only
 
        /* Check to see if we have indexes in need of defrag; otherwise, re-scan the database(s) */
        If Not Exists(Select Top 1 * From dbo.dba_indexDefragStatus Where defragDate Is Null)
            Or @forceRescan = 1
        Begin
 
            /* Truncate our list of indexes to prepare for a new scan */
            Truncate Table dbo.dba_indexDefragStatus;
 
            If @debugMode = 1 RaisError('Looping through our list of databases and checking for fragmentation...', 0, 42) With NoWait;
 
            /* Loop through our list of databases */
            While (Select Count(*) From #databaseList Where scanStatus = 0) > 0
            Begin
 
                Select Top 1 @databaseID = databaseID
                From #databaseList
                Where scanStatus = 0;
 
                Select @debugMessage = '  working on ' + DB_Name(@databaseID) + '...';
 
                If @debugMode = 1
                    RaisError(@debugMessage, 0, 42) With NoWait;
 
               /* Determine which indexes to defrag using our user-defined parameters */
                Insert Into dbo.dba_indexDefragStatus
                (
                      databaseID
                    , databaseName
                    , objectID
                    , indexID
                    , partitionNumber
                    , fragmentation
                    , page_count
                    , range_scan_count
                    , scanDate
                )
                Select
                      ps.database_id As 'databaseID'
                    , QuoteName(DB_Name(ps.database_id)) As 'databaseName'
                    , ps.object_id As 'objectID'
                    , ps.index_id As 'indexID'
                    , ps.partition_number As 'partitionNumber'
                    , Sum(ps.avg_fragmentation_in_percent) As 'fragmentation'
                    , Sum(ps.page_count) As 'page_count'
                    , os.range_scan_count
                    , GetDate() As 'scanDate'
                From sys.dm_db_index_physical_stats(@databaseID, Object_Id(@tableName), Null , Null, @scanMode) As ps
                Join sys.dm_db_index_operational_stats(@databaseID, Object_Id(@tableName), Null , Null) as os
                    On ps.database_id = os.database_id
                    And ps.object_id = os.object_id
                    and ps.index_id = os.index_id
                    And ps.partition_number = os.partition_number
                Where avg_fragmentation_in_percent >= @minFragmentation 
                    And ps.index_id > 0 -- ignore heaps
                    And ps.page_count > @minPageCount 
                    And ps.index_level = 0 -- leaf-level nodes only, supports @scanMode
                Group By ps.database_id 
                    , QuoteName(DB_Name(ps.database_id)) 
                    , ps.object_id 
                    , ps.index_id 
                    , ps.partition_number 
                    , os.range_scan_count
                Option (MaxDop 2);
 
                /* Do we want to exclude right-most populated partition of our partitioned indexes? */
                If @excludeMaxPartition = 1
                Begin
 
                    Set @excludeMaxPartitionSQL = '
                        Select ' + Cast(@databaseID As varchar(10)) + ' As [databaseID]
                            , [object_id]
                            , index_id
                            , Max(partition_number) As [maxPartition]
                        From ' + DB_Name(@databaseID) + '.sys.partitions
                        Where partition_number > 1
                            And [rows] > 0
                        Group By object_id
                            , index_id;';
 
                    Insert Into #maxPartitionList
                    Execute sp_executesql @excludeMaxPartitionSQL;
 
                End;
 
                /* Keep track of which databases have already been scanned */
                Update #databaseList
                Set scanStatus = 1
                Where databaseID = @databaseID;
 
            End
 
            /* We don't want to defrag the right-most populated partition, so
               delete any records for partitioned indexes where partition = Max(partition) */
            If @excludeMaxPartition = 1
            Begin
 
                Delete ids
                From dbo.dba_indexDefragStatus As ids
                Join #maxPartitionList As mpl
                    On ids.databaseID = mpl.databaseID
                    And ids.objectID = mpl.objectID
                    And ids.indexID = mpl.indexID
                    And ids.partitionNumber = mpl.maxPartition;
 
            End;
 
            /* Update our exclusion mask for any index that has a restriction on the days it can be defragged */
            Update ids
            Set ids.exclusionMask = ide.exclusionMask
            From dbo.dba_indexDefragStatus As ids
            Join dbo.dba_indexDefragExclusion As ide
                On ids.databaseID = ide.databaseID
                And ids.objectID = ide.objectID
                And ids.indexID = ide.indexID;
 
        End
 
        Select @debugMessage = 'Looping through our list... there are ' + Cast(Count(*) As varchar(10)) + ' indexes to defrag!'
        From dbo.dba_indexDefragStatus
        Where defragDate Is Null
            And page_count Between @minPageCount And IsNull(@maxPageCount, page_count);
 
        If @debugMode = 1 RaisError(@debugMessage, 0, 42) With NoWait;
 
        /* Begin our loop for defragging */
        While (Select Count(*) 
               From dbo.dba_indexDefragStatus 
               Where (
                           (@executeSQL = 1 And defragDate Is Null) 
                        Or (@executeSQL = 0 And defragDate Is Null And printStatus = 0)
                     )
                And exclusionMask & Power(2, DatePart(weekday, GetDate())-1) = 0
                And page_count Between @minPageCount And IsNull(@maxPageCount, page_count)) > 0
        Begin
 
            /* Check to see if we need to exit our loop because of our time limit */        
            If IsNull(@endDateTime, GetDate()) < GetDate()
            Begin
                RaisError('Our time limit has been exceeded!', 11, 42) With NoWait;
            End;
 
            If @debugMode = 1 RaisError('  Picking an index to beat into shape...', 0, 42) With NoWait;
 
            /* Grab the index with the highest priority, based on the values submitted; 
               Look at the exclusion mask to ensure it can be defragged today */
            Set @getIndexSQL = N'
            Select Top 1 
                  @objectID_Out         = objectID
                , @indexID_Out          = indexID
                , @databaseID_Out       = databaseID
                , @databaseName_Out     = databaseName
                , @fragmentation_Out    = fragmentation
                , @partitionNumber_Out  = partitionNumber
                , @pageCount_Out        = page_count
            From dbo.dba_indexDefragStatus
            Where defragDate Is Null ' 
                + Case When @executeSQL = 0 Then 'And printStatus = 0' Else '' End + '
                And exclusionMask & Power(2, DatePart(weekday, GetDate())-1) = 0
                And page_count Between @p_minPageCount and IsNull(@p_maxPageCount, page_count)
            Order By + ' + @defragOrderColumn + ' ' + @defragSortOrder;
 
            Set @getIndexSQL_Param = N'@objectID_Out        int OutPut
                                     , @indexID_Out         int OutPut
                                     , @databaseID_Out      int OutPut
                                     , @databaseName_Out    nvarchar(128) OutPut
                                     , @fragmentation_Out   int OutPut
                                     , @partitionNumber_Out int OutPut
                                     , @pageCount_Out       int OutPut
                                     , @p_minPageCount      int
                                     , @p_maxPageCount      int';
 
            Execute sp_executesql @getIndexSQL
                , @getIndexSQL_Param
                , @p_minPageCount       = @minPageCount
                , @p_maxPageCount       = @maxPageCount
                , @objectID_Out         = @objectID OutPut
                , @indexID_Out          = @indexID OutPut
                , @databaseID_Out       = @databaseID OutPut
                , @databaseName_Out     = @databaseName OutPut
                , @fragmentation_Out    = @fragmentation OutPut
                , @partitionNumber_Out  = @partitionNumber OutPut
                , @pageCount_Out        = @pageCount OutPut;
 
            If @debugMode = 1 RaisError('  Looking up the specifics for our index...', 0, 42) With NoWait;
 
            /* Look up index information */
            Select @updateSQL = N'Update ids
                Set schemaName = QuoteName(s.name)
                    , objectName = QuoteName(o.name)
                    , indexName = QuoteName(i.name)
                From dbo.dba_indexDefragStatus As ids
                Inner Join ' + @databaseName + '.sys.objects As o
                    On ids.objectID = o.object_id
                Inner Join ' + @databaseName + '.sys.indexes As i
                    On o.object_id = i.object_id
                    And ids.indexID = i.index_id
                Inner Join ' + @databaseName + '.sys.schemas As s
                    On o.schema_id = s.schema_id
                Where o.object_id = ' + Cast(@objectID As varchar(10)) + '
                    And i.index_id = ' + Cast(@indexID As varchar(10)) + '
                    And i.type > 0
                    And ids.databaseID = ' + Cast(@databaseID As varchar(10));
 
            Execute sp_executesql @updateSQL;
 
            /* Grab our object names */
            Select @objectName  = objectName
                , @schemaName   = schemaName
                , @indexName    = indexName
            From dbo.dba_indexDefragStatus
            Where objectID = @objectID
                And indexID = @indexID
                And databaseID = @databaseID;
 
            If @debugMode = 1 RaisError('  Grabbing the partition count...', 0, 42) With NoWait;
 
            /* Determine if the index is partitioned */
            Select @partitionSQL = 'Select @partitionCount_OUT = Count(*)
                                        From ' + @databaseName + '.sys.partitions
                                        Where object_id = ' + Cast(@objectID As varchar(10)) + '
                                            And index_id = ' + Cast(@indexID As varchar(10)) + ';'
                , @partitionSQL_Param = '@partitionCount_OUT int OutPut';
 
            Execute sp_executesql @partitionSQL, @partitionSQL_Param, @partitionCount_OUT = @partitionCount OutPut;
 
            If @debugMode = 1 RaisError('  Seeing if there are any LOBs to be handled...', 0, 42) With NoWait;
 
            /* Determine if the table contains LOBs */
            Select @LOB_SQL = ' Select @containsLOB_OUT = Count(*)
                                From ' + @databaseName + '.sys.columns With (NoLock) 
                                Where [object_id] = ' + Cast(@objectID As varchar(10)) + '
                                   And (system_type_id In (34, 35, 99)
                                            Or max_length = -1);'
                                /*  system_type_id --> 34 = image, 35 = text, 99 = ntext
                                    max_length = -1 --> varbinary(max), varchar(max), nvarchar(max), xml */
                    , @LOB_SQL_Param = '@containsLOB_OUT int OutPut';
 
            Execute sp_executesql @LOB_SQL, @LOB_SQL_Param, @containsLOB_OUT = @containsLOB OutPut;
 
            If @debugMode = 1 RaisError('  Checking for indexes that do not allow page locks...', 0, 42) With NoWait;
 
            /* Determine if page locks are allowed; for those indexes, we need to always rebuild */
            Select @allowPageLockSQL = 'Select @allowPageLocks_OUT = Count(*)
                                        From ' + @databaseName + '.sys.indexes
                                        Where object_id = ' + Cast(@objectID As varchar(10)) + '
                                            And index_id = ' + Cast(@indexID As varchar(10)) + '
                                            And Allow_Page_Locks = 0;'
                , @allowPageLockSQL_Param = '@allowPageLocks_OUT int OutPut';
 
            Execute sp_executesql @allowPageLockSQL, @allowPageLockSQL_Param, @allowPageLocks_OUT = @allowPageLocks OutPut;
 
            If @debugMode = 1 RaisError('  Building our SQL statements...', 0, 42) With NoWait;
 
            /* If there's not a lot of fragmentation, or if we have a LOB, we should reorganize */
            If (@fragmentation < @rebuildThreshold Or @containsLOB >= 1 Or @partitionCount > 1)
                And @allowPageLocks = 0
            Begin
 
                Set @sqlCommand = N'Alter Index ' + @indexName + N' On ' + @databaseName + N'.' 
                                    + @schemaName + N'.' + @objectName + N' ReOrganize';
 
                /* If our index is partitioned, we should always reorganize */
                If @partitionCount > 1
                    Set @sqlCommand = @sqlCommand + N' Partition = ' 
                                    + Cast(@partitionNumber As nvarchar(10));
 
            End
            /* If the index is heavily fragmented and doesn't contain any partitions or LOB's, 
               or if the index does not allow page locks, rebuild it */
            Else If (@fragmentation >= @rebuildThreshold Or @allowPageLocks <> 0)
                And IsNull(@containsLOB, 0) != 1 And @partitionCount <= 1
            Begin
 
                /* Set online rebuild options; requires Enterprise Edition */
                If @onlineRebuild = 1 And @editionCheck = 1 
                    Set @rebuildCommand = N' Rebuild With (Online = On';
                Else
                    Set @rebuildCommand = N' Rebuild With (Online = Off';
 
                /* Set sort operation preferences */
                If @sortInTempDB = 1 
                    Set @rebuildCommand = @rebuildCommand + N', Sort_In_TempDB = On';
                Else
                    Set @rebuildCommand = @rebuildCommand + N', Sort_In_TempDB = Off';
 
                /* Set processor restriction options; requires Enterprise Edition */
                If @maxDopRestriction Is Not Null And @editionCheck = 1
                    Set @rebuildCommand = @rebuildCommand + N', MaxDop = ' + Cast(@maxDopRestriction As varchar(2)) + N')';
                Else
                    Set @rebuildCommand = @rebuildCommand + N')';
 
                Set @sqlCommand = N'Alter Index ' + @indexName + N' On ' + @databaseName + N'.'
                                + @schemaName + N'.' + @objectName + @rebuildCommand;
 
            End
            Else
                /* Print an error message if any indexes happen to not meet the criteria above */
                If @printCommands = 1 Or @debugMode = 1
                    RaisError('We are unable to defrag this index.', 0, 42) With NoWait;
 
            /* Are we executing the SQL?  If so, do it */
            If @executeSQL = 1
            Begin
 
                Set @debugMessage = 'Executing: ' + @sqlCommand;
 
                /* Print the commands we're executing if specified to do so */
                If @printCommands = 1 Or @debugMode = 1
                    RaisError(@debugMessage, 0, 42) With NoWait;
 
                /* Grab the time for logging purposes */
                Set @dateTimeStart  = GetDate();
 
                /* Log our actions */
                Insert Into dbo.dba_indexDefragLog
                (
                      databaseID
                    , databaseName
                    , objectID
                    , objectName
                    , indexID
                    , indexName
                    , partitionNumber
                    , fragmentation
                    , page_count
                    , dateTimeStart
                    , sqlStatement
                )
                Select
                      @databaseID
                    , @databaseName
                    , @objectID
                    , @objectName
                    , @indexID
                    , @indexName
                    , @partitionNumber
                    , @fragmentation
                    , @pageCount
                    , @dateTimeStart
                    , @sqlCommand;
 
                Set @indexDefrag_id = Scope_Identity();
 
                /* Wrap our execution attempt in a try/catch and log any errors that occur */
                Begin Try
 
                    /* Execute our defrag! */
                    Execute sp_executesql @sqlCommand;
                    Set @dateTimeEnd = GetDate();
 
                    /* Update our log with our completion time */
                    Update dbo.dba_indexDefragLog
                    Set dateTimeEnd = @dateTimeEnd
                        , durationSeconds = DateDiff(second, @dateTimeStart, @dateTimeEnd)
                    Where indexDefrag_id = @indexDefrag_id;
 
                End Try
                Begin Catch
 
                    /* Update our log with our error message */
                    Update dbo.dba_indexDefragLog
                    Set dateTimeEnd = GetDate()
                        , durationSeconds = -1
                        , errorMessage = Error_Message()
                    Where indexDefrag_id = @indexDefrag_id;
 
                    If @debugMode = 1 
                        RaisError('  An error has occurred executing this command! Please review the dba_indexDefragLog table for details.'
                            , 0, 42) With NoWait;
 
                End Catch
 
                /* Just a little breather for the server */
                WaitFor Delay @defragDelay;
 
                Update dbo.dba_indexDefragStatus
                Set defragDate = GetDate()
                    , printStatus = 1
                Where databaseID       = @databaseID
                  And objectID         = @objectID
                  And indexID          = @indexID
                  And partitionNumber  = @partitionNumber;
 
            End
            Else
            /* Looks like we're not executing, just printing the commands */
            Begin
                If @debugMode = 1 RaisError('  Printing SQL statements...', 0, 42) With NoWait;
 
                If @printCommands = 1 Or @debugMode = 1 
                    Print IsNull(@sqlCommand, 'error!');
 
                Update dbo.dba_indexDefragStatus
                Set printStatus = 1
                Where databaseID       = @databaseID
                  And objectID         = @objectID
                  And indexID          = @indexID
                  And partitionNumber  = @partitionNumber;
            End
 
        End
 
        /* Do we want to output our fragmentation results? */
        If @printFragmentation = 1
        Begin
 
            If @debugMode = 1 RaisError('  Displaying a summary of our action...', 0, 42) With NoWait;
 
            Select databaseID
                , databaseName
                , objectID
                , objectName
                , indexID
                , indexName
                , partitionNumber
                , fragmentation
                , page_count
                , range_scan_count
            From dbo.dba_indexDefragStatus
            Where defragDate >= @startDateTime
            Order By defragDate;
 
        End;
 
    End Try
    Begin Catch
 
        Set @debugMessage = Error_Message() + ' (Line Number: ' + Cast(Error_Line() As varchar(10)) + ')';
        Print @debugMessage;
 
    End Catch;
 
    /* When everything is said and done, make sure to get rid of our temp table */
    Drop Table #databaseList;
    Drop Table #processor;
    Drop Table #maxPartitionList;
 
    If @debugMode = 1 RaisError('DONE!  Thank you for taking care of your indexes!  :)', 0, 42) With NoWait;
 
    Set NoCount Off;
    Return 0
End

You can also download it here: dba_indexDefrag_sp_v40_public.txt

I’ve had this latest version in production on terabyte-size databases running SQL Server 2005 and 2008 Enterprise editions for the last 3 months, where it runs nightly without issue. I’ve also had numerous beta testers report success in their environments, too. But to be safe, make sure to keep an eye on it the first time it runs to ensure you understand the impact on your server.

Enjoy!

Michelle

Page Splitting & Rollbacks

So while I was at the grocery store last night, my mind wandered to SQL Server. This time, I was pondering what happens to a page split if the transaction is rolled back. I didn’t know the answer, but my guess was that the page split remained, since it would be less expensive for SQL Server to leave the data where it was sitting. Also, in theory, if the page split occurred once, it could need to occur again, so why undergo that same expense twice?

I decided to run a simple test to see what would happen. First, I created a really wide table and tossed 4 rows into it:

Create Table myTable
(
      id            int Primary Key
    , wideColumn    char(2000) 
);
 
Insert Into myTable
Select 1, Replicate('A', 2000) Union All
Select 2, Replicate('B', 2000) Union All
Select 4, Replicate('C', 2000) Union All
Select 5, Replicate('D', 2000);

I left an open spot for id=3, so I can force a page split. Next, I looked at the page data using the script I posted in February.

Here’s what I saw:

Before

Before

Pay attention to the 2 items boxed in red. m_slotCnt tells us how many records are on the page, and m_nextPage tells us the address of the next page. As you may have guessed, a m_nextPage value of 0:0 means you’re looking at the last page allocated to the object.

Now let’s insert a record, roll it back, and see what happens:

Begin Transaction;
 
Insert Into myTable
Select 3, Replicate('E', 2000);
 
Rollback Transaction;

I ran my DBCC Page command again and here’s what I saw:

After

After

As you can see, m_slotCnt is now 2, and m_nextPage is no longer 0:0 (although your actual page number will probably be different than mine). If I pull up the new page, I find my 2 relocated records, id’s 4 and 5.

So what’s this all mean? In short, page splits are NOT reversed when a transaction is rolled back. Why should you care? Well, you probably wouldn’t care much, unless you roll back a lot of transactions. But this is also a good thing to keep in mind if you have to abort a really large insert or update; if you don’t plan to re-execute the aborted script, you may want to defrag your indexes to fix the splits.

Source: http://sqlfool.com/2009/04/page-splitting-rollbacks/

Automated Index Defrag Script

UPDATE: This script has been significantly updated. Please view the latest version at http://sqlfool.com/2011/06/index-defrag-script-v4-1/.

So after much delay, here’s the latest and greatest version of my index defrag script.

A summary of the changes:

  • Added support for centralized execution. Option to defrag indexes for a single database from another database, or for all non-system databases.
  • Consolidated Enterprise and Standard versions of the script with new @editionCheck variable.
  • Added parametrization for MaxDop restrictions during rebuilds; validates that the value does not exceed the actual number of processors on the server.
  • Changed minimum fragmentation default value from 10 to 5 to match BOL recommendations.
  • Limited defrags to objects with more than 8 pages.
  • Added a debug option to give a little more insight into what’s happening and to assist with troubleshooting.
  • Updated logic for handling partitions and LOBs.

And a couple of notes and explanations:

Don’t you know you can just pass NULL to sys.dm_db_index_physical_stats for the DatabaseID?
Yes, I realize you can do this. But I don’t want to defrag the system databases, i.e. tempdb, so I opted to handle it this way instead.

How long will this take?
It depends. I don’t necessarily recommend running it without specifying a database; at least, not unmonitored. You *can* do that, but it could take a while. For example, to run sys.dm_db_index_physical_stats for all databases and tables, totaling 2TB, took me 4.5 hours; that doesn’t even count the actual defrags.

Where should I put this?
It’s up to you. If you have a database for items like centralized maintenance or scratch tables, that may be a good place for it. If you prefer, you could also put this in each individual database and call it locally, too. I would not put this in the master or msdb databases.

This is pretty close to a complete rewrite, so please let me know if you encounter any bugs. And now… the code!

If Not Exists(Select [object_id] From sys.tables Where name = N'dba_indexDefragLog')
Begin
    -- Drop Table dbo.dba_indexDefragLog
    Create Table dbo.dba_indexDefragLog
    (
          indexDefrag_id    int identity(1,1)   Not Null
        , databaseID        int                 Not Null
        , databaseName      nvarchar(128)       Not Null
        , objectID          int                 Not Null
        , objectName        nvarchar(128)       Not Null
        , indexID           int                 Not Null
        , indexName         nvarchar(128)       Not Null
        , partitionNumber   smallint            Not Null
        , fragmentation     float               Not Null
        , page_count        int                 Not Null
        , dateTimeStart     datetime            Not Null
        , durationSeconds   int                 Not Null
        Constraint PK_indexDefragLog Primary Key Clustered (indexDefrag_id)
    )
 
    Print 'dba_indexDefragLog Table Created';
End
 
If ObjectProperty(Object_ID('dbo.dba_indexDefrag_sp'), N'IsProcedure') = 1
Begin
    Drop Procedure dbo.dba_indexDefrag_sp;
    Print 'Procedure dba_indexDefrag_sp dropped';
End;
Go
 
 
Create Procedure dbo.dba_indexDefrag_sp
 
    /* Declare Parameters */
      @minFragmentation     float           = 5.0  
        /* in percent, will not defrag if fragmentation less than specified */
    , @rebuildThreshold     float           = 30.0  
        /* in percent, greater than @rebuildThreshold will result in rebuild instead of reorg */
    , @executeSQL           bit             = 1     
        /* 1 = execute; 0 = print command only */
    , @database             varchar(128)    = Null
        /* Option to specify a database name; null will return all */
    , @tableName            varchar(4000)   = Null  -- databaseName.schema.tableName
        /* Option to specify a table name; null will return all */
    , @onlineRebuild        bit             = 1     
        /* 1 = online rebuild; 0 = offline rebuild; only in Enterprise */
    , @maxDopRestriction    tinyint         = Null
        /* Option to restrict the number of processors for the operation; only in Enterprise */
    , @printCommands        bit             = 0     
        /* 1 = print commands; 0 = do not print commands */
    , @printFragmentation   bit             = 0
        /* 1 = print fragmentation prior to defrag; 
           0 = do not print */
    , @defragDelay          char(8)         = '00:00:05'
        /* time to wait between defrag commands */
    , @debugMode            bit             = 0
        /* display some useful comments to help determine if/where issues occur */
As
/*********************************************************************************
    Name:       dba_indexDefrag_sp
 
    Author:     Michelle Ufford, http://sqlfool.com
 
    Purpose:    Defrags all indexes for one or more databases
 
    Notes:
 
    CAUTION: TRANSACTION LOG SIZE MUST BE MONITORED CLOSELY WHEN DEFRAGMENTING.
 
      @minFragmentation     defaulted to 10%, will not defrag if fragmentation 
                            is less than that
 
      @rebuildThreshold     defaulted to 30% as recommended by Microsoft in BOL;
                            greater than 30% will result in rebuild instead
 
      @executeSQL           1 = execute the SQL generated by this proc; 
                            0 = print command only
 
      @database             Optional, specify specific database name to defrag;
                            If not specified, all non-system databases will
                            be defragged.
 
      @tableName            Specify if you only want to defrag indexes for a 
                            specific table, format = databaseName.schema.tableName;
                            if not specified, all tables will be defragged.
 
      @onlineRebuild        1 = online rebuild; 
                            0 = offline rebuild
 
      @maxDopRestriction    Option to specify a processor limit for index rebuilds
 
      @printCommands        1 = print commands to screen; 
                            0 = do not print commands
 
      @printFragmentation   1 = print fragmentation to screen;
                            0 = do not print fragmentation
 
      @defragDelay          time to wait between defrag commands; gives the
                            server a little time to catch up 
 
      @debugMode            1 = display debug comments; helps with troubleshooting
                            0 = do not display debug comments
 
    Called by:  SQL Agent Job or DBA
 
    Date        Initials	Description
    ----------------------------------------------------------------------------
    2008-10-27  MFU         Initial Release for public consumption
    2008-11-17  MFU         Added page-count to log table
                            , added @printFragmentation option
    2009-03-17  MFU         Provided support for centralized execution, 
                            , consolidated Enterprise & Standard versions
                            , added @debugMode, @maxDopRestriction
                            , modified LOB and partition logic                            
*********************************************************************************
    Exec dbo.dba_indexDefrag_sp
          @executeSQL           = 0
        , @minFragmentation     = 80
        , @printCommands        = 1
        , @debugMode            = 1
        , @printFragmentation   = 1
        , @database             = 'AdventureWorks'
        , @tableName            = 'AdventureWorks.Sales.SalesOrderDetail';
*********************************************************************************/																
 
Set NoCount On;
Set XACT_Abort On;
Set Quoted_Identifier On;
 
Begin
 
    If @debugMode = 1 RaisError('Dusting off the spiderwebs and starting up...', 0, 42) With NoWait;
 
    /* Declare our variables */
    Declare   @objectID             int
            , @databaseID           int
            , @databaseName         nvarchar(128)
            , @indexID              int
            , @partitionCount       bigint
            , @schemaName           nvarchar(128)
            , @objectName           nvarchar(128)
            , @indexName            nvarchar(128)
            , @partitionNumber      smallint
            , @partitions           smallint
            , @fragmentation        float
            , @pageCount            int
            , @sqlCommand           nvarchar(4000)
            , @rebuildCommand       nvarchar(200)
            , @dateTimeStart        datetime
            , @dateTimeEnd          datetime
            , @containsLOB          bit
            , @editionCheck         bit
            , @debugMessage         varchar(128)
            , @updateSQL            nvarchar(4000)
            , @partitionSQL         nvarchar(4000)
            , @partitionSQL_Param   nvarchar(1000)
            , @LOB_SQL              nvarchar(4000)
            , @LOB_SQL_Param        nvarchar(1000);
 
    /* Create our temporary tables */
    Create Table #indexDefragList
    (
          databaseID        int
        , databaseName      nvarchar(128)
        , objectID          int
        , indexID           int
        , partitionNumber   smallint
        , fragmentation     float
        , page_count        int
        , defragStatus      bit
        , schemaName        nvarchar(128)   Null
        , objectName        nvarchar(128)   Null
        , indexName         nvarchar(128)   Null
    );
 
    Create Table #databaseList
    (
          databaseID        int
        , databaseName      varchar(128)
    );
 
    Create Table #processor 
    (
          [index]           int
        , Name              varchar(128)
        , Internal_Value    int
        , Character_Value   int
    );
 
    If @debugMode = 1 RaisError('Beginning validation...', 0, 42) With NoWait;
 
    /* Just a little validation... */
    If @minFragmentation Not Between 0.00 And 100.0
        Set @minFragmentation = 5.0;
 
    If @rebuildThreshold Not Between 0.00 And 100.0
        Set @rebuildThreshold = 30.0;
 
    If @defragDelay Not Like '00:[0-5][0-9]:[0-5][0-9]'
        Set @defragDelay = '00:00:05';
 
    /* Make sure we're not exceeding the number of processors we have available */
    Insert Into #processor
    Execute xp_msver 'ProcessorCount';
 
    If @maxDopRestriction Is Not Null And @maxDopRestriction > (Select Internal_Value From #processor)
        Select @maxDopRestriction = Internal_Value
        From #processor;
 
    /* Check our server version; 1804890536 = Enterprise, 610778273 = Enterprise Evaluation, -2117995310 = Developer */
    If (Select ServerProperty('EditionID')) In (1804890536, 610778273, -2117995310) 
        Set @editionCheck = 1 -- supports online rebuilds
    Else
        Set @editionCheck = 0; -- does not support online rebuilds
 
    If @debugMode = 1 RaisError('Grabbing a list of our databases...', 0, 42) With NoWait;
 
    /* Retrieve the list of databases to investigate */
    Insert Into #databaseList
    Select database_id
        , name
    From sys.databases
    Where name = IsNull(@database, name)
        And database_id > 4 -- exclude system databases
        And [state] = 0; -- state must be ONLINE
 
    If @debugMode = 1 RaisError('Looping through our list of databases and checking for fragmentation...', 0, 42) With NoWait;
 
    /* Loop through our list of databases */
    While (Select Count(*) From #databaseList) > 0
    Begin
 
        Select Top 1 @databaseID = databaseID
        From #databaseList;
 
        Select @debugMessage = '  working on ' + DB_Name(@databaseID) + '...';
 
        If @debugMode = 1
            RaisError(@debugMessage, 0, 42) With NoWait;
 
       /* Determine which indexes to defrag using our user-defined parameters */
        Insert Into #indexDefragList
        Select
              database_id As databaseID
            , QuoteName(DB_Name(database_id)) As 'databaseName'
            , [object_id] As objectID
            , index_id As indexID
            , partition_number As partitionNumber
            , avg_fragmentation_in_percent As fragmentation
            , page_count 
            , 0 As 'defragStatus' /* 0 = unprocessed, 1 = processed */
            , Null As 'schemaName'
            , Null As 'objectName'
            , Null As 'indexName'
        From sys.dm_db_index_physical_stats (@databaseID, Object_Id(@tableName), Null , Null, N'Limited')
        Where avg_fragmentation_in_percent >= @minFragmentation 
            And index_id > 0 -- ignore heaps
            And page_count > 8 -- ignore objects with less than 1 extent
        Option (MaxDop 1);
 
        Delete From #databaseList
        Where databaseID = @databaseID;
 
    End
 
    Create Clustered Index CIX_temp_indexDefragList
        On #indexDefragList(databaseID, objectID, indexID, partitionNumber);
 
    Select @debugMessage = 'Looping through our list... there''s ' + Cast(Count(*) As varchar(10)) + ' indexes to defrag!'
    From #indexDefragList;
 
    If @debugMode = 1 RaisError(@debugMessage, 0, 42) With NoWait;
 
    /* Begin our loop for defragging */
    While (Select Count(*) From #indexDefragList Where defragStatus = 0) > 0
    Begin
 
        If @debugMode = 1 RaisError('  Picking an index to beat into shape...', 0, 42) With NoWait;
 
        /* Grab the most fragmented index first to defrag */
        Select Top 1 
              @objectID         = objectID
            , @indexID          = indexID
            , @databaseID       = databaseID
            , @databaseName     = databaseName
            , @fragmentation    = fragmentation
            , @partitionNumber  = partitionNumber
            , @pageCount        = page_count
        From #indexDefragList
        Where defragStatus = 0
        Order By fragmentation Desc;
 
        If @debugMode = 1 RaisError('  Looking up the specifics for our index...', 0, 42) With NoWait;
 
        /* Look up index information */
        Select @updateSQL = N'Update idl
            Set schemaName = QuoteName(s.name)
                , objectName = QuoteName(o.name)
                , indexName = QuoteName(i.name)
            From #indexDefragList As idl
            Inner Join ' + @databaseName + '.sys.objects As o
                On idl.objectID = o.object_id
            Inner Join ' + @databaseName + '.sys.indexes As i
                On o.object_id = i.object_id
            Inner Join ' + @databaseName + '.sys.schemas As s
                On o.schema_id = s.schema_id
            Where o.object_id = ' + Cast(@objectID As varchar(10)) + '
                And i.index_id = ' + Cast(@indexID As varchar(10)) + '
                And i.type > 0
                And idl.databaseID = ' + Cast(@databaseID As varchar(10));
 
        Execute sp_executeSQL @updateSQL;
 
        /* Grab our object names */
        Select @objectName  = objectName
            , @schemaName   = schemaName
            , @indexName    = indexName
        From #indexDefragList
        Where objectID = @objectID
            And indexID = @indexID
            And databaseID = @databaseID;
 
        If @debugMode = 1 RaisError('  Grabbing the partition count...', 0, 42) With NoWait;
 
        /* Determine if the index is partitioned */
        Select @partitionSQL = 'Select @partitionCount_OUT = Count(*)
                                    From ' + @databaseName + '.sys.partitions
                                    Where object_id = ' + Cast(@objectID As varchar(10)) + '
                                        And index_id = ' + Cast(@indexID As varchar(10)) + ';'
            , @partitionSQL_Param = '@partitionCount_OUT int OutPut';
 
        Execute sp_executeSQL @partitionSQL, @partitionSQL_Param, @partitionCount_OUT = @partitionCount OutPut;
 
        If @debugMode = 1 RaisError('  Seeing if there''s any LOBs to be handled...', 0, 42) With NoWait;
 
        /* Determine if the table contains LOBs */
        Select @LOB_SQL = ' Select Top 1 @containsLOB_OUT = column_id
                            From ' + @databaseName + '.sys.columns With (NoLock) 
                            Where [object_id] = ' + Cast(@objectID As varchar(10)) + '
                                And (system_type_id In (34, 35, 99)
                                        Or max_length = -1);'
                            /*  system_type_id --> 34 = image, 35 = text, 99 = ntext
                                max_length = -1 --> varbinary(max), varchar(max), nvarchar(max), xml */
                , @LOB_SQL_Param = '@containsLOB_OUT int OutPut';
 
        Execute sp_executeSQL @LOB_SQL, @LOB_SQL_Param, @containsLOB_OUT = @containsLOB OutPut;
 
        If @debugMode = 1 RaisError('  Building our SQL statements...', 0, 42) With NoWait;
 
        /* If there's not a lot of fragmentation, or if we have a LOB, we should reorganize */
        If @fragmentation < @rebuildThreshold Or @containsLOB = 1 Or @partitionCount > 1
        Begin
 
            Set @sqlCommand = N'Alter Index ' + @indexName + N' On ' + @databaseName + N'.' 
                                + @schemaName + N'.' + @objectName + N' ReOrganize';
 
            /* If our index is partitioned, we should always reorganize */
            If @partitionCount > 1
                Set @sqlCommand = @sqlCommand + N' Partition = ' 
                                + Cast(@partitionNumber As nvarchar(10));
 
        End;
 
        /* If the index is heavily fragmented and doesn't contain any partitions or LOB's, rebuild it */
        If @fragmentation >= @rebuildThreshold And IsNull(@containsLOB, 0) != 1 And @partitionCount <= 1
        Begin
 
            /* Set online rebuild options; requires Enterprise Edition */
            If @onlineRebuild = 1 And @editionCheck = 1 
                Set @rebuildCommand = N' Rebuild With (Online = On';
            Else
                Set @rebuildCommand = N' Rebuild With (Online = Off';
 
            /* Set processor restriction options; requires Enterprise Edition */
            If @maxDopRestriction Is Not Null And @editionCheck = 1
                Set @rebuildCommand = @rebuildCommand + N', MaxDop = ' + Cast(@maxDopRestriction As varchar(2)) + N')';
            Else
                Set @rebuildCommand = @rebuildCommand + N')';
 
            Set @sqlCommand = N'Alter Index ' + @indexName + N' On ' + @databaseName + N'.'
                            + @schemaName + N'.' + @objectName + @rebuildCommand;
 
        End;
 
        /* Are we executing the SQL?  If so, do it */
        If @executeSQL = 1
        Begin
 
            If @debugMode = 1 RaisError('  Executing SQL statements...', 0, 42) With NoWait;
 
            /* Grab the time for logging purposes */
            Set @dateTimeStart  = GetDate();
            Execute sp_executeSQL @sqlCommand;
            Set @dateTimeEnd  = GetDate();
 
            /* Log our actions */
            Insert Into dbo.dba_indexDefragLog
            (
                  databaseID
                , databaseName
                , objectID
                , objectName
                , indexID
                , indexName
                , partitionNumber
                , fragmentation
                , page_count
                , dateTimeStart
                , durationSeconds
            )
            Select
                  @databaseID
                , @databaseName
                , @objectID
                , @objectName
                , @indexID
                , @indexName
                , @partitionNumber
                , @fragmentation
                , @pageCount
                , @dateTimeStart
                , DateDiff(second, @dateTimeStart, @dateTimeEnd);
 
            /* Just a little breather for the server */
            WaitFor Delay @defragDelay;
 
            /* Print if specified to do so */
            If @printCommands = 1
                Print N'Executed: ' + @sqlCommand;
        End
        Else
        /* Looks like we're not executing, just printing the commands */
        Begin
            If @debugMode = 1 RaisError('  Printing SQL statements...', 0, 42) With NoWait;
 
            If @printCommands = 1 Print IsNull(@sqlCommand, 'error!');
        End
 
        If @debugMode = 1 RaisError('  Updating our index defrag status...', 0, 42) With NoWait;
 
        /* Update our index defrag list so we know we've finished with that index */
        Update #indexDefragList
        Set defragStatus = 1
        Where databaseID       = @databaseID
          And objectID         = @objectID
          And indexID          = @indexID
          And partitionNumber  = @partitionNumber;
 
    End
 
    /* Do we want to output our fragmentation results? */
    If @printFragmentation = 1
    Begin
 
        If @debugMode = 1 RaisError('  Displaying fragmentation results...', 0, 42) With NoWait;
 
        Select databaseID
            , databaseName
            , objectID
            , objectName
            , indexID
            , indexName
            , fragmentation
            , page_count
        From #indexDefragList;
 
    End;
 
    /* When everything is said and done, make sure to get rid of our temp table */
    Drop Table #indexDefragList;
    Drop Table #databaseList;
    Drop Table #processor;
 
    If @debugMode = 1 RaisError('DONE!  Thank you for taking care of your indexes!  :)', 0, 42) With NoWait;
 
    Set NoCount Off;
	Return 0
End
Go

Thanks to my beta testers, @scoinva, @davidmtate, @jdanton, and @SuperCoolMoss!
Special thanks to SCM for keeping on me to finish this.

Happy Defragging!

Michelle

Source: http://sqlfool.com/2009/03/automated-index-defrag-script/

Index Fragmentation PotW Webcast – Now Available

The Pain-of-the-Week webcast I did last Thursday is now online! You can find it here: http://www.quest.com/common/registration.aspx?requestdefid=23092.

The topic of the webcast is index fragmentation: what is it, how to identify it, and how to fix it. You can find the materials for this webcast in my previous blog post. I’ll also be updating SQLServerPedia with the materials, hopefully tonight.

Thanks to the great feedback I’ve received, I’ll be doing another Pain-of-the-Week webcast, this time with Brent Ozar. More info to follow as we hammer out the specifics.

In a related note, I have updated my index defrag script. I’m just waiting for my awesome beta testers to let me know everything works for them. It works just fine on my servers (lol) but I don’t have access to any Standard editions, etc., so I just want to be extra sure before I unleash it on the SQL world. I should have it online tomorrow.

Source: http://sqlfool.com/2009/03/index-fragmentation-potw-webcast/

Fragmentation on Replicated Tables

I’ve heard more than one person state that they do not need to defrag their tables, because they’re replicated and the source tables are defragged regularly. Let’s set this myth straight.

Repeat after me: defragmentation processes are not replicated.

Good. Thank you.

For those non-believers, let me prove it:

SET NOCOUNT ON;
 
/* Create publication db */
CREATE DATABASE sandbox_publisher;
GO
 
/* Create subscription db */
CREATE DATABASE sandbox_subscriber;
GO
 
/* Navigate to publisher db */
USE sandbox_publisher;
GO
 
/* Create a table to play with */
CREATE TABLE myTable
(
      myID UNIQUEIDENTIFIER
    , myColumn VARCHAR(2000)
 
    CONSTRAINT PK_myTable PRIMARY KEY CLUSTERED (myID)
);
/* NOTE: please never, ever use this
   type of clustered index in real-life.
   The whole purpose is to generate
   substantial fragmentation for 
   illustrative purposes. */
 
/* Populate it with some non-sequential
   records to generate fragmentation */
DECLARE @iteration INT;
SET @iteration = 0;
 
WHILE @iteration < 1000
BEGIN
    INSERT INTO myTable
    SELECT NewID(), REPLICATE('A', 2000);
 
    SET @iteration = @iteration + 1;
END
 
/* Now let's verify that we really did
   make a mess of our clustered index */
SELECT avg_fragmentation_in_percent
    , page_count
FROM sys.dm_db_index_physical_stats 
(DB_ID(), OBJECT_ID(N'MyTable'), NULL , NULL, N'Limited') 
OPTION (MaxDop 1);
 
/* Results:
 
avg_fragmentation_in_percent page_count
---------------------------- --------------------
99.0157480314961             508
 
99% fragmented, not too shabby!  Your results 
may vary slightly, based on the guid values
generated by NewID().
*/
 
/* Now, let's set up replication */
USE sandbox_publisher;
GO
 
/* Enable publication */
EXECUTE SP_REPLICATIONDBOPTION
      @dbname = N'sandbox_publisher'
    , @optname = N'publish'
    , @VALUE = N'true';
GO
 
/* Create our publication */
EXECUTE SP_ADDPUBLICATION
      @publication = N'myTestPublication' 
    , @sync_method = N'concurrent'
    , @description = N'Test Publication'
    , @status = N'active'
    , @independent_agent = N'true'
    , @immediate_sync = N'true'
    , @retention = 0
GO
 
/* Create our snapshot agent */
EXECUTE SP_ADDPUBLICATION_SNAPSHOT
      @publication = N'myTestPublication'
    , @frequency_type = 1;
 
/* Add our table as an article */
EXECUTE SP_ADDARTICLE
      @publication = N'myTestPublication'
    , @article = N'myTable'
    , @source_owner = N'dbo'
    , @source_object = N'myTable'
    , @type = N'logbased'
    , @destination_table = N'myTable'
    , @destination_owner = N'dbo'
    , @ins_cmd = N'CALL sp_MSins_dbomyTable'
    , @del_cmd = N'CALL sp_MSdel_dbomyTable'
    , @upd_cmd = N'MCALL sp_MSupd_dbomyTable';
GO
 
/* Generate an initial snapshot */
EXECUTE sp_startpublication_snapshot
      @publication = N'myTestPublication';
 
/* Create our subscription */
EXECUTE SP_ADDSUBSCRIPTION 
      @publication = N'myTestPublication'
    , @subscriber = N'YourServerName'
    , @destination_db = N'sandbox_subscriber';
 
/* At this point, basic transactional replication 
   should be configured.  You should now have a 
   copy of myTable in your subscription database. */
 
USE sandbox_subscriber;
GO
 
/* Let's take a look at fragmentation on the 
   subscription database. */
SELECT avg_fragmentation_in_percent
    , page_count
FROM sys.dm_db_index_physical_stats 
(DB_ID(), OBJECT_ID(N'MyTable'), NULL , NULL, N'Limited') 
OPTION (MaxDop 1);
 
/* Results:
 
avg_fragmentation_in_percent page_count
---------------------------- --------------------
0.29940119760479             334
 
Less than 1% fragmented!  Why is this?  During
initialization, a copy of the schema and data
is sent to the subscriber.  The data is sorted
before insertion into the destination table.
*/
 
USE sandbox_publisher;
GO
 
/* Let's insert another 1000 records and see
   what happens... */
DECLARE @iteration INT;
SET @iteration = 0;
 
WHILE @iteration < 1000
BEGIN
    INSERT INTO sandbox_publisher.dbo.myTable
    SELECT NewID(), REPLICATE('A', 2000);
 
    SET @iteration = @iteration + 1;
END
 
SELECT avg_fragmentation_in_percent
    , page_count
FROM sys.dm_db_index_physical_stats 
(DB_ID(), OBJECT_ID(N'MyTable'), NULL , NULL, N'Limited') 
OPTION (MaxDop 1);
 
/* Results:
 
avg_fragmentation_in_percent page_count
---------------------------- --------------------
98.6193293885602             1014
 
The publisher is still very fragmented 
(as expected) */
 
USE sandbox_subscriber;
GO
 
SELECT avg_fragmentation_in_percent
    , page_count
FROM sys.dm_db_index_physical_stats 
(DB_ID(), OBJECT_ID(N'MyTable'), NULL , NULL, N'Limited') 
OPTION (MaxDop 1);
 
/* Results:
 
avg_fragmentation_in_percent page_count
---------------------------- --------------------
95.4034729315628             979
 
But now the subscriber is fragmented too!  This
is because each individual transaction is 
replicated, so out-of-order inserts affect
both the publishing and the subcribing 
databases equally.
*/
 
/* Finally, let's rebuild our index on the 
   publisher and see what happens */
USE sandbox_publisher;
GO
 
ALTER INDEX PK_myTable ON myTable Rebuild;
 
SELECT avg_fragmentation_in_percent
    , page_count
FROM sys.dm_db_index_physical_stats 
(DB_ID(), OBJECT_ID(N'MyTable'), NULL , NULL, N'Limited') 
OPTION (MaxDop 1);
 
/* Results:
 
avg_fragmentation_in_percent page_count
---------------------------- --------------------
0                            667
 
0% fragmentation in the publishing table!  
What about our subscribing table?
*/
 
USE sandbox_subscriber;
GO
 
SELECT avg_fragmentation_in_percent
    , page_count
FROM sys.dm_db_index_physical_stats 
(DB_ID(), OBJECT_ID(N'MyTable'), NULL , NULL, N'Limited') 
OPTION (MaxDop 1);
 
/* Results:
 
avg_fragmentation_in_percent page_count
---------------------------- --------------------
95.4034729315628             979
 
As you can see, the subcribing table was
completely unaffected by the defrag
activities on the publisher.
*/

So there you have it, proof that defrag operations are not replicated! Now go defrag your replicated tables. :)

Oh, and if you need help defragging your indexes, check out my index defrag script (2005, 2008).