When working with Performance Monitor (perfmon) on Windows Server 2008, you might encounter the frustrating error message: "The Data Collector Set or one of its dependencies is already in use.". This typically occurs when attempting to start a newly created Data Collector Set (DCS).

From my experience troubleshooting similar issues, these are the most frequent scenarios:

• Another instance of perfmon is running the same DCS
• The DCS was improperly terminated in a previous session
• System resources are locked by another performance monitoring tool
• Permission issues with the output location

Before diving into solutions, let's verify the exact state of your performance monitoring:

logman query -ets

This command will list all running Event Trace Sessions. Look for any entries that might be using your target DCS.

If you identify a stuck session, use this PowerShell command to terminate it:

Stop-PerfCollectorSet -Name "YourCollectorSetName" -Force

Alternatively, the command-line approach:

logman stop "YourCollectorSetName" -ets
logman delete "YourCollectorSetName"

In persistent cases, you might need to clean up registry entries:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger]
"YourCollectorSetName"=-

Warning: Always back up your registry before making changes.

Here's a complete PowerShell script I've used to handle this issue:

function Reset-PerfmonSessions {
    param(
        [string]$CollectorSetName
    )
    
    try {
        # Stop if running
        logman stop $CollectorSetName -ErrorAction SilentlyContinue
        
        # Delete existing
        logman delete $CollectorSetName -ErrorAction SilentlyContinue
        
        # Clean up potential registry residue
        $regPath = "HKLM:\SYSTEM\CurrentControlSet\Control\WMI\Autologger"
        if (Test-Path "$regPath\$CollectorSetName") {
            Remove-Item -Path "$regPath\$CollectorSetName" -Force
        }
        
        # Restart the service for good measure
        Restart-Service -Name "pla" -Force
        
        return $true
    }
    catch {
        Write-Error $_.Exception.Message
        return $false
    }
}

To avoid this issue in the future:

• Always properly stop DCS through perfmon UI or logman stop
• Implement unique naming for your collector sets
• Consider adding error handling to your monitoring scripts

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When working with Performance Monitor (Perfmon) on Windows Server 2008, you might encounter the frustrating error: "The Data Collector Set or one of its dependencies is already in use.". This typically occurs when attempting to start a newly created Data Collector Set (DCS).

The issue often manifests in environments with:

• Identically configured virtual machines (where it works on one but not another)
• Previously terminated DCS sessions that didn't clean up properly
• Conflicting performance counters
• Permission issues with the Performance Log Users group

Before diving deep, try these PowerShell commands to check active collectors:

# List all running data collector sets
Get-WmiObject -Namespace "root\cimv2" -Class "Win32_PerfFormattedData" | 
Where-Object {$_.Name -like "*YourCollectorSetName*"}

# Alternative method using logman
logman query -ets

Here's a step-by-step method to resolve the issue:

1. Force Stop All Running Collectors

# PowerShell command to stop all running collectors
Get-WmiObject -Namespace "root\cimv2" -Class "Win32_PerfFormattedData" | 
ForEach-Object {
    if ($_.Name -match "YourCollectorSetName") {
        $_.Stop()
    }
}

# Alternative using logman
logman stop "YourCollectorSetName" -ets
logman delete "YourCollectorSetName"

2. Reset Performance Counters

# Rebuild performance counters
lodctr /r

# For more thorough reset
unlodctr /q
lodctr /q

3. Check for File Locks

The DCS might be locked due to output files. Check with:

# PowerShell to find locked files
$handleExe = "$env:SystemRoot\System32\handle.exe"
if (Test-Path $handleExe) {
    & $handleExe -a "YourCollectorSetName"
} else {
    Write-Warning "Handle.exe not found in System32"
}

For recurring issues, create this PowerShell script:

# Perfmon DCS Cleanup Script
$collectorName = "YourCollectorSetName"

try {
    # Stop if running
    logman stop $collectorName -ets -ErrorAction SilentlyContinue
    
    # Delete existing
    logman delete $collectorName -ErrorAction SilentlyContinue
    
    # Recreate with proper permissions
    $user = "$env:USERDOMAIN\$env:USERNAME"
    logman create counter $collectorName -o "C:\PerfLogs\$collectorName.blg" -f bin -si 15 --v -c "\Processor(_Total)\% Processor Time" "\Memory\Available MBytes" -u $user
    
    # Start fresh
    logman start $collectorName
    
    Write-Host "Successfully reset $collectorName" -ForegroundColor Green
} catch {
    Write-Error "Failed to reset collector: $_"
}

If the issue persists, examine these areas:

• Windows Event Viewer logs (Application and System)
• Resource Monitor for handle conflicts
• Process Explorer for detailed process information

To avoid future occurrences:

# Scheduled task to clean up stale collectors
$action = New-ScheduledTaskAction -Execute "logman.exe" -Argument "stop YourCollectorSetName -ets"
$trigger = New-ScheduledTaskTrigger -AtLogOn
Register-ScheduledTask -TaskName "PerfmonCleanup" -Action $action -Trigger $trigger -RunLevel Highest