functions/Invoke-DbaDbShrink.ps1
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function Invoke-DbaDbShrink { <# .SYNOPSIS Shrinks all files in a database. This is a command that should rarely be used. - Shrinks can cause severe index fragmentation (to the tune of 99%) - Shrinks can cause massive growth in the database's transaction log - Shrinks can require a lot of time and system resources to perform data movement .DESCRIPTION Shrinks all files in a database. Databases should be shrunk only when completely necessary. Many awesome SQL people have written about why you should not shrink your data files. Paul Randal and Kalen Delaney wrote great posts about this topic: http://www.sqlskills.com/blogs/paul/why-you-should-not-shrink-your-data-files http://sqlmag.com/sql-server/shrinking-data-files However, there are some cases where a database will need to be shrunk. In the event that you must shrink your database: 1. Ensure you have plenty of space for your T-Log to grow 2. Understand that shrinks require a lot of CPU and disk resources 3. Consider running DBCC INDEXDEFRAG or ALTER INDEX ... REORGANIZE after the shrink is complete. .PARAMETER SqlInstance The target SQL Server instance or instances. Defaults to the default instance on localhost. .PARAMETER SqlCredential Login to the target instance using alternative credentials. Windows and SQL Authentication supported. Accepts credential objects (Get-Credential). .PARAMETER Database The database(s) to process - this list is auto-populated from the server. If unspecified, all databases will be processed. .PARAMETER ExcludeDatabase The database(s) to exclude - this list is auto-populated from the server. .PARAMETER AllUserDatabases Run command against all user databases. .PARAMETER PercentFreeSpace Specifies how much free space to leave, defaults to 0. .PARAMETER ShrinkMethod Specifies the method that is used to shrink the database Default Data in pages located at the end of a file is moved to pages earlier in the file. Files are truncated to reflect allocated space. EmptyFile Migrates all of the data from the referenced file to other files in the same filegroup. (DataFile and LogFile objects only). NoTruncate Data in pages located at the end of a file is moved to pages earlier in the file. TruncateOnly Data distribution is not affected. Files are truncated to reflect allocated space, recovering free space at the end of any file. .PARAMETER StatementTimeout Timeout in minutes. Defaults to infinity (shrinks can take a while). .PARAMETER LogsOnly Deprecated. Use FileType instead. .PARAMETER FileType Specifies the files types that will be shrunk All - All Data and Log files are shrunk, using database shrink (Default) Data - Just the Data files are shrunk using file shrink Log - Just the Log files are shrunk using file shrink .PARAMETER StepSize Measured in bits - but no worries! PowerShell has a very cool way of formatting bits. Just specify something like: 1MB or 10GB. See the examples for more information. If specified, this will chunk a larger shrink operation into multiple smaller shrinks. If shrinking a file by a large amount there are benefits of doing multiple smaller chunks. .PARAMETER ExcludeIndexStats Exclude statistics about fragmentation. .PARAMETER ExcludeUpdateUsage Exclude DBCC UPDATE USAGE for database. .PARAMETER WhatIf Shows what would happen if the command were to run. .PARAMETER Confirm Prompts for confirmation of every step. For example: Are you sure you want to perform this action? Performing the operation "Shrink database" on target "pubs on SQL2016\VNEXT". [Y] Yes [A] Yes to All [N] No [L] No to All [S] Suspend [?] Help (default is "Y"): .PARAMETER EnableException By default, when something goes wrong we try to catch it, interpret it and give you a friendly warning message. This avoids overwhelming you with "sea of red" exceptions, but is inconvenient because it basically disables advanced scripting. Using this switch turns this "nice by default" feature off and enables you to catch exceptions with your own try/catch. .NOTES Tags: Shrink, Database Author: Chrissy LeMaire (@cl), netnerds.net Website: https://dbatools.io Copyright: (c) 2018 by dbatools, licensed under MIT License: MIT https://opensource.org/licenses/MIT .LINK https://dbatools.io/Invoke-DbaDbShrink .EXAMPLE PS C:\> Invoke-DbaDbShrink -SqlInstance sql2016 -Database Northwind,pubs,Adventureworks2014 Shrinks Northwind, pubs and Adventureworks2014 to have as little free space as possible. .EXAMPLE PS C:\> Invoke-DbaDbShrink -SqlInstance sql2014 -Database AdventureWorks2014 -PercentFreeSpace 50 Shrinks AdventureWorks2014 to have 50% free space. So let's say AdventureWorks2014 was 1GB and it's using 100MB space. The database free space would be reduced to 50MB. .EXAMPLE PS C:\> Invoke-DbaDbShrink -SqlInstance sql2014 -Database AdventureWorks2014 -PercentFreeSpace 50 -FileType Data -StepSize 25MB Shrinks AdventureWorks2014 to have 50% free space, runs shrinks in 25MB chunks for improved performance. .EXAMPLE PS C:\> Invoke-DbaDbShrink -SqlInstance sql2012 -AllUserDatabases Shrinks all databases on SQL2012 (not ideal for production) #> [CmdletBinding(SupportsShouldProcess = $true, ConfirmImpact = 'Low')] param ( [parameter(Mandatory, ValueFromPipeline)] [Alias("ServerInstance", "SqlServer")] [DbaInstanceParameter[]]$SqlInstance, [Alias("Credential")] [PSCredential]$SqlCredential, [Alias("Databases")] [object[]]$Database, [object[]]$ExcludeDatabase, [switch]$AllUserDatabases, [ValidateRange(0, 99)] [int]$PercentFreeSpace = 0, [ValidateSet('Default', 'EmptyFile', 'NoTruncate', 'TruncateOnly')] [string]$ShrinkMethod = "Default", [ValidateSet('All', 'Data', 'Log')] [string]$FileType = "All", [int]$StepSize, [int]$StatementTimeout = 0, [switch]$LogsOnly, [switch]$ExcludeIndexStats, [switch]$ExcludeUpdateUsage, [Alias('Silent')] [switch]$EnableException ) begin { if ($LogsOnly) { Test-DbaDeprecation -DeprecatedOn "1.0.0" -Parameter "LogsOnly" $FileType = 'Log' } if (-not $Database -and -not $ExcludeDatabase -and -not $AllUserDatabases) { Stop-Function -Message "You must specify databases to execute against using either -Database, -Exclude or -AllUserDatabases" return } if ((Test-Bound -ParameterName StepSize) -and $stepsize -lt 1024) { Stop-Function -Message "StepSize is measured in bits. Did you mean $StepSize bits? If so, please use 1024 or above. If not, then use the PowerShell bit notation like $($StepSize)MB or $($StepSize)GB" return } if ($stepsize) { $StepSizeKB = ([dbasize]($StepSize)).Kilobyte } $StatementTimeoutSeconds = $StatementTimeout * 60 $sql = "SELECT avg(avg_fragmentation_in_percent) as [avg_fragmentation_in_percent] , max(avg_fragmentation_in_percent) as [max_fragmentation_in_percent] FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL, NULL, NULL) AS indexstats WHERE indexstats.avg_fragmentation_in_percent > 0 AND indexstats.page_count > 100 GROUP BY indexstats.database_id" } process { if (Test-FunctionInterrupt) { return } foreach ($instance in $SqlInstance) { try { $server = Connect-SqlInstance -SqlInstance $instance -SqlCredential $SqlCredential } catch { Stop-Function -Message "Failure" -Category ConnectionError -ErrorRecord $_ -Target $instance -Continue } $server.ConnectionContext.StatementTimeout = $StatementTimeoutSeconds Write-Message -Level Verbose -Message "Connection timeout set to $StatementTimeout" $dbs = $server.Databases | Where-Object {$_.IsAccessible} if ($Database) { $dbs = $dbs | Where-Object Name -In $Database } if ($ExcludeDatabase) { $dbs = $dbs | Where-Object Name -NotIn $ExcludeDatabase } foreach ($db in $dbs) { Write-Message -Level Verbose -Message "Processing $db on $instance" if ($db.IsDatabaseSnapshot) { Write-Message -Level Warning -Message "The database $db on server $instance is a snapshot and cannot be shrunk. Skipping database." continue } $files = @() if ($FileType -in ('Log', 'All')) { $files += $db.LogFiles } if ($FileType -in ('Data', 'All')) { $files += $db.FileGroups.Files } foreach ($file in $files) { $startingSize = $file.Size $spaceUsed = $file.UsedSpace $spaceAvailable = ($file.Size - $file.UsedSpace) $desiredSpaceAvailable = [math]::ceiling((($PercentFreeSpace / 100)) * $spaceUsed) $desiredFileSize = $spaceUsed + $desiredSpaceAvailable Write-Message -Level Verbose -Message "File: $($file.Name)" Write-Message -Level Verbose -Message "Initial Size (KB): $([int]$startingSize)" Write-Message -Level Verbose -Message "Space Used (KB): $([int]$spaceUsed)" Write-Message -Level Verbose -Message "Initial Freespace (KB): $([int]$spaceAvailable)" Write-Message -Level Verbose -Message "Target Freespace (KB): $([int]$desiredSpaceAvailable)" Write-Message -Level Verbose -Message "Target FileSize (KB): $([int]$desiredFileSize)" if ($spaceAvailable -le $desiredSpaceAvailable) { Write-Message -Level Warning -Message "File size of ($startingSize) is less than or equal to the desired outcome ($desiredFileSize) for $($file.Name)" } else { if ($Pscmdlet.ShouldProcess("$db on $instance", "Shrinking from $([int]$startingSize)KB to $([int]$desiredFileSize)KB")) { if ($server.VersionMajor -gt 8 -and $ExcludeIndexStats -eq $false) { Write-Message -Level Verbose -Message "Getting starting average fragmentation" $dataRow = $server.Query($sql, $db.name) $startingFrag = $dataRow.avg_fragmentation_in_percent $startingTopFrag = $dataRow.max_fragmentation_in_percent } else { $startingTopFrag = $startingFrag = $null } $start = Get-Date try { Write-Message -Level Verbose -Message "Beginning shrink of files" $shrinkGap = ($startingSize - $desiredFileSize) Write-Message -Level Verbose -Message "ShrinkGap: $([int]$shrinkGap) KB" Write-Message -Level Verbose -Message "Step Size: $(([dbasize]$StepSize).Megabyte) MB" if ($StepSizeKB -and ($shrinkGap -gt $stepSizeKB)) { for ($i = 1; $i -le [int](($shrinkGap) / $stepSizeKB); $i++) { Write-Message -Level Verbose -Message "Step: $i" $shrinkSize = $startingSize - (($StepSizeKB * 1024 * 1024) * $i) if ($shrinkSize -lt $desiredFileSize) { $shrinkSize = $desiredFileSize } Write-Message -Level Verbose -Message ("Shrinking {0} to {1}" -f $file.Name, $shrinkSize) $file.Shrink(($shrinkSize / 1024), $ShrinkMethod) $file.Refresh() if ($startingSize -eq $file.Size) { Write-Message -Level Verbose -Message ("Unable to shrink further") break } } } else { $file.Shrink(($desiredFileSize / 1024), $ShrinkMethod) $file.Refresh() } $success = $true } catch { $success = $false Stop-Function -message "Failure" -EnableException $EnableException -ErrorRecord $_ -Continue continue } $end = Get-Date $finalFileSize = $file.Size $finalSpaceAvailable = ($file.Size - $file.UsedSpace) Write-Message -Level Verbose -Message "Final file size: $([int]$finalFileSize) KB" Write-Message -Level Verbose -Message "Final file space available: $($finalSpaceAvailable) KB" if ($server.VersionMajor -gt 8 -and $ExcludeIndexStats -eq $false -and $success -and $FileType -ne 'Log') { Write-Message -Level Verbose -Message "Getting ending average fragmentation" $dataRow = $server.Query($sql, $db.name) $endingDefrag = $dataRow.avg_fragmentation_in_percent $endingTopDefrag = $dataRow.max_fragmentation_in_percent } else { $endingTopDefrag = $endingDefrag = $null } $timSpan = New-TimeSpan -Start $start -End $end $ts = [TimeSpan]::fromseconds($timSpan.TotalSeconds) $elapsed = "{0:HH:mm:ss}" -f ([datetime]$ts.Ticks) $object = [PSCustomObject]@{ ComputerName = $server.ComputerName InstanceName = $server.ServiceName SqlInstance = $server.DomainInstanceName Database = $db.name File = $file.name Start = $start End = $end Elapsed = $elapsed Success = $success InitialSize = [dbasize]($startingSize * 1024) InitialUsed = [dbasize]($spaceUsed * 1024) InitialAvailable = [dbasize]($spaceAvailable * 1024) TargetAvailable = [dbasize]($desiredSpaceAvailable * 1024) FinalAvailable = [dbasize]($finalSpaceAvailable * 1024) FinalSize = [dbasize]($finalFileSize * 1024) InitialAverageFragmentation = [math]::Round($startingFrag, 1) FinalAverageFragmentation = [math]::Round($endingDefrag, 1) InitialTopFragmentation = [math]::Round($startingTopFrag, 1) FinalTopFragmentation = [math]::Round($endingTopDefrag, 1) Notes = "Database shrinks can cause massive index fragmentation and negatively impact performance. You should now run DBCC INDEXDEFRAG or ALTER INDEX ... REORGANIZE" } if ($ExcludeIndexStats) { Select-DefaultView -InputObject $object -ExcludeProperty InitialAverageFragmentation, FinalAverageFragmentation, InitialTopFragmentation, FinalTopFragmentation } else { $object } } } } } } } end { Test-DbaDeprecation -DeprecatedOn "1.0.0" -Alias Invoke-DbaDatabaseShrink } } |