How to fix Error 5064 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: Error 5064 – Database Changes Blocked in Single-User Mode

Why This Error Happens

This error occurs because the database is currently configured with ALTER DATABASE ... SET SINGLE_USER, which restricts access to only one connection at a time. When your session is not that single active connection—or when a previous session terminated without properly releasing the lock—SQL Server blocks any further state or option changes to protect data integrity. This is common after maintenance tasks like restoring a database, running DBCC CHECKDB with repair options, or renaming a database, where the single-user flag was never reset to MULTI_USER afterward.

Step-by-Step Resolution Guide

Step 1: Identify Active Connections to the Database

  • Open SQL Server Management Studio (SSMS) or Azure Data Studio and connect to the instance.
  • Run the following query to check current session usage:
  SELECT session_id, login_name, status, program_name 
  FROM sys.dm_exec_sessions 
  WHERE database_id = DB_ID('YourDatabaseName');
  • Note the session_id of any connection currently locking the database.

Step 2: Terminate Conflicting Sessions

  • If an orphaned session is holding the single-user slot, kill it using its session ID.
  • Execute the kill command in a new query window:
  KILL <session_id>;
  • Ensure no other applications (like SSMS Object Explorer tabs) are silently holding open connections to the target database.

Step 3: Reset the Database to Multi-User Mode

  • Open a new query window connected to the master database (not the target database itself).
  • Run the following command to force the change and roll back any incomplete transactions:
  ALTER DATABASE YourDatabaseName SET MULTI_USER WITH ROLLBACK IMMEDIATE;
  • Confirm the command completes without returning Error 5064 again.

Step 4: Check for Windows Server Resource Locks

  • On Windows Server 2025, verify that no antivirus or backup agent (like Windows Server Backup VSS writer) is locking the .mdf or .ldf files.
  • Navigate to Task Manager > Details and ensure sqlservr.exe does not have a hung child process preventing the state change.
  • Restart the SQL Server (MSSQLSERVER) service via services.msc if the lock persists after the rollback command.

Alternative or Verification Steps

  • Verify the Fix: Run SELECT name, user_access_desc FROM sys.databases WHERE name = 'YourDatabaseName'; to confirm the user_access_desc column now reads MULTI_USER.
  • Alternative Fix: If the ALTER DATABASE command hangs indefinitely, restart the SQL Server service entirely via PowerShell using Restart-Service -Name 'MSSQLSERVER' -Force, which will clear all active single-user locks upon reboot.