functions/Get-DbaLatchStatistic.ps1
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function Get-DbaLatchStatistic { <# .SYNOPSIS Displays latch statistics from sys.dm_os_latch_stats .DESCRIPTION This command is based off of Paul Randal's post "Advanced SQL Server performance tuning" Returns: LatchClass WaitSeconds WaitCount Percentage AverageWaitSeconds URL Reference: https://www.sqlskills.com/blogs/paul/advanced-performance-troubleshooting-waits-latches-spinlocks/ https://www.sqlskills.com/blogs/paul/most-common-latch-classes-and-what-they-mean/ .PARAMETER SqlInstance The SQL Server instance. Server version must be SQL Server version 2005 or higher. .PARAMETER SqlCredential Login to the target instance using alternative credentials. Windows and SQL Authentication supported. Accepts credential objects (Get-Credential) .PARAMETER Threshold Threshold, in percentage of all latch stats on the system. Default per Paul's post is 95%. .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: LatchStatistics, Waits Author: Patrick Flynn (@sqllensman) Website: https://dbatools.io Copyright: (c) 2018 by dbatools, licensed under MIT License: MIT https://opensource.org/licenses/MIT .LINK https://dbatools.io/Get-DbaLatchStatistic .EXAMPLE PS C:\> Get-DbaLatchStatistic -SqlInstance sql2008, sqlserver2012 Check latch statistics for servers sql2008 and sqlserver2012 .EXAMPLE PS C:\> Get-DbaLatchStatistic -SqlInstance sql2008 -Threshold 98 Check latch statistics on server sql2008 for thresholds above 98% .EXAMPLE PS C:\> $output = Get-DbaLatchStatistic -SqlInstance sql2008 -Threshold 100 | Select * | ConvertTo-DbaDataTable Collects all latch statistics on server sql2008 into a Data Table. .EXAMPLE PS C:\> 'sql2008','sqlserver2012' | Get-DbaLatchStatistic Get latch statistics for servers sql2008 and sqlserver2012 via pipline .EXAMPLE PS C:\> $cred = Get-Credential sqladmin PS C:\> Get-DbaLatchStatistic -SqlInstance sql2008 -SqlCredential $cred Connects using sqladmin credential and returns latch statistics from sql2008 .EXAMPLE PS C:\> $output = Get-DbaLatchStatistic -SqlInstance sql2008 PS C:\> $output PS C:\> foreach ($row in ($output | Sort-Object -Unique Url)) { Start-Process ($row).Url } Displays the output then loads the associated sqlskills website for each result. Opens one tab per unique URL. #> [CmdletBinding()] param ( [parameter(Mandatory, ValueFromPipeline)] [Alias("ServerInstance", "SqlServer", "SqlServers")] [DbaInstance[]]$SqlInstance, [PSCredential]$SqlCredential, [int]$Threshold = 95, [Alias('Silent')] [switch]$EnableException ) BEGIN { $sql = "WITH [Latches] AS ( SELECT [latch_class], [wait_time_ms] / 1000.0 AS [WaitS], [waiting_requests_count] AS [WaitCount], Case WHEN SUM ([wait_time_ms]) OVER() = 0 THEN NULL ELSE 100.0 * [wait_time_ms] / SUM ([wait_time_ms]) OVER() END AS [Percentage], ROW_NUMBER() OVER(ORDER BY [wait_time_ms] DESC) AS [RowNum] FROM sys.dm_os_latch_stats WHERE [latch_class] NOT IN (N'BUFFER') ) SELECT MAX ([W1].[latch_class]) AS [LatchClass], CAST (MAX ([W1].[WaitS]) AS DECIMAL(14, 2)) AS [WaitSeconds], MAX ([W1].[WaitCount]) AS [WaitCount], CAST (MAX ([W1].[Percentage]) AS DECIMAL(14, 2)) AS [Percentage], CAST ((MAX ([W1].[WaitS]) / MAX ([W1].[WaitCount])) AS DECIMAL (14, 4)) AS [AvgWaitSeconds], CAST ('https://www.sqlskills.com/help/latches/' + MAX ([W1].[latch_class]) as XML) AS [URL] FROM [Latches] AS [W1] INNER JOIN [Latches] AS [W2] ON [W2].[RowNum] <= [W1].[RowNum] GROUP BY [W1].[RowNum] HAVING SUM ([W2].[Percentage]) - MAX ([W1].[Percentage]) < $Threshold;" Write-Message -Level Debug -Message $sql } process { if (Test-FunctionInterrupt) { return } foreach ($instance in $SqlInstance) { Write-Message -Level Verbose -Message "Connecting to $instance" try { $server = Connect-SqlInstance -SqlInstance $instance -SqlCredential $SqlCredential -MinimumVersion 9 } catch { Stop-Function -Message "Failure" -Category ConnectionError -ErrorRecord $_ -Target $instance -Continue Return } Write-Message -Level Verbose -Message "Connected to $instance" foreach ($row in $server.Query($sql)) { [PSCustomObject]@{ ComputerName = $server.NetName InstanceName = $server.ServiceName SqlInstance = $server.DomainInstanceName WaitType = $row.LatchClass WaitSeconds = $row.WaitSeconds WaitCount = $row.WaitCount Percentage = $row.Percentage AverageWaitSeconds = $row.AvgWaitSeconds URL = $row.URL } } } } } |