How to fix Error 1494 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: Error 1494 — Database Mirroring Conflict with Change Event Streaming

Why This Error Happens

This error occurs because SQL Server 2025 introduces Change Event Streaming (CES) as a native feature, and it is architecturally incompatible with the legacy Database Mirroring technology due to conflicting transaction log reader requirements. Both features require exclusive low-level access to the transaction log stream to track changes, and SQL Server blocks the mirroring setup to prevent log corruption or duplicate change-tracking states. Essentially, the database engine detects an active CES session on the target database and refuses to initialize the mirroring endpoint until that conflict is resolved.

Step-by-Step Resolution Guide

Step 1: Verify the Current Change Event Streaming Status

  • Open SQL Server Management Studio (SSMS) or Azure Data Studio connected to the SQL Server 2025 instance.
  • Run the following query to check the CES state for the specific database:
  SELECT name, is_change_event_streaming_enabled 
  FROM sys.databases 
  WHERE name = 'YourDatabaseName';
  • Confirm the output returns 1 (enabled), which confirms the root cause of Error 1494.

Step 2: Disable Change Event Streaming on the Target Database

  • Execute the following T-SQL command to disable CES before configuring mirroring:
  ALTER DATABASE YourDatabaseName 
  SET CHANGE_EVENT_STREAMING = OFF;
  • Ensure no active applications or Event Hub/Kafka connectors are actively consuming the stream during this change to avoid data gaps.
  • Wait for the command to complete; this may take a moment if there is a large backlog of unread change events.

Step 3: Re-attempt the Database Mirroring Configuration

  • Navigate to SSMS, right-click the database, select Tasks > Mirror, and proceed with the setup wizard.
  • Alternatively, run the manual partner configuration command:
  ALTER DATABASE YourDatabaseName 
  SET PARTNER = 'TCP://PartnerServer.domain.com:5022';
  • Confirm the mirroring state changes to SYNCHRONIZED or SYNCHRONIZING in the Database Properties window.

Step 4: Evaluate Migration to Always On Availability Groups (Recommended)

  • Since Database Mirroring is a deprecated feature, check if your environment can support Always On Availability Groups instead, as this feature is fully compatible with Change Event Streaming.
  • Use the Always On Availability Group Wizard in SSMS to migrate the setup without needing to disable CES.

Alternative or Verification Steps

  • Verify the fix: Re-run the sys.databases query from Step 1; the is_change_event_streaming_enabled column should show 0, and the mirroring status in the SSMS Object Explorer should no longer show a red “error” icon.
  • Alternative solution: If CES is a business requirement that cannot be disabled, do not use legacy Mirroring; instead, configure Always On Availability Groups (Step 4) as it supports simultaneous high-availability and change streaming without this restriction.