How to fix Error 3409 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 3409 — Performance Counter Shared Memory Setup Failed

Why This Error Happens

Error 3409 occurs when SQL Server 2025 cannot initialize the shared memory segment used by Windows Performance Monitor counters, typically because the registry performance counter strings are corrupted or out of sync with the sqlctr.ini/sqlctr.xml definition files. This can also happen if the SQL Server service account lacks the necessary registry permissions under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\<InstanceID>\Performance, or if a prior failed install/patch left orphaned or mismatched counter DLL references. In some cases, third-party monitoring agents or antivirus software lock the shared memory handles, preventing SQL Server from registering its counters at startup.

Step-by-Step Resolution Guide

Step 1: Verify and Repair Registry Permissions

  • Open regedit and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\<InstanceID>\Performance.
  • Right-click the key, select Permissions, and confirm the SQL Server service account has Full Control.
  • If the key is missing entirely, this confirms counter registration never completed and you must proceed to reinstalling the counters (Step 2).

Step 2: Unload and Reload Performance Counters

  • Open an elevated Command Prompt and navigate to C:\Program Files\Microsoft SQL Server\MSSQL17.<InstanceID>\MSSQL\Binn\.
  • Unload the existing (potentially corrupted) counters: unlodctr MSSQL$<InstanceID> (or unlodctr MSSQLSERVER for default instance).
  • Reload the counters using the instance-specific .ini file: lodctr sqlctr.ini.
  • Restart the SQL Server () service via services.msc or net stop/start.

Step 3: Rebuild the Entire Performance Counter Library (if Step 2 fails)

  • Run lodctr /R from an elevated prompt to rebuild the full counter registry from stored INI definitions across all installed applications.
  • If corruption is severe, run exctrlst.exe (Extensible Counter List) to confirm MSSQL$<InstanceID> appears as “Active” with no error flags.
  • As a last resort, re-run SQL Server Setup → Repair for the affected instance to force regeneration of sqlctr.ini and re-register the performance DLL (sqlctr160.dll or newer).

Step 4: Check for File System or Antivirus Interference

  • Confirm sqlctr.ini exists in the Binn directory and is not flagged as read-only or quarantined by antivirus.
  • Add an exclusion for the SQL Server Binn directory in Windows Defender or your third-party AV product.
  • Re-attempt Step 2 after clearing any file locks (use Process Explorer to confirm no process is holding a handle on sqlctr.ini).

Alternative or Verification Steps

  • Open Performance Monitor (perfmon.exe), click Add Counter, and confirm SQLServer:General Statistics (or your instance-specific object) appears in the list without errors — this confirms the shared memory segment is functioning.
  • If the error persists after a full repair, check the SQL Server Error Log and Windows Application Event Log for correlating Event ID 3409 timestamps to rule out concurrent WMI provider or Resource Monitor conflicts, then consider rebuilding the instance’s performance DLLs via a full uninstall/reinstall of that feature component.