WinCC Redundancy in Workgroup: DCOM setup

Setting Up WinCC 7.5 Hot Standby Redundancy in Workgroup: Step-by-Step Guide

A ceramics plant has been running a SCADA system on Siemens WinCC 7.0 since 2013. The hardware setup uses HP ProLiant DL380p Gen8 servers with Windows Server 2008R2 and S7-300/400 controllers. The goal: upgrade to WinCC 7.5 SP2 Update 15 on Windows Server 2012R2 without new hardware, implement hot standby redundancy across two servers in workgroup mode, and ensure seamless failover on the client station.

We cloned the system onto two identical servers after an interim upgrade. A dedicated backbone network (10.10.10.x) handles heartbeat between servers, while the main network (192.168.0.x) manages data sync and PLC communication. The client runs WinCC Runtime Advanced with automatic server switching.

Server and Network Configuration

| Component | Server 1 | Server 2 | Client |

|-----------|----------|----------|--------|

| Name | SCADASERVER1 | SCADASERVER2 | SCADACLIENT0 |

| OS | Windows Server 2012R2 | Windows Server 2012R2 | Windows Server 2012R2 |

| WinCC | 7.5 SP2 Upd15 | 7.5 SP2 Upd15 | 7.5 SP2 Upd15 (Client) |

| SQL | 2016 SP3 | 2016 SP3 | 2016 SP3 |

| Main Network | 192.168.0.1 | 192.168.0.2 | 192.168.0.3 |

| Backbone | 10.10.10.1 | 10.10.10.2 | — |

The backbone uses a direct connection for partner status monitoring, while tag and archive sync occurs over the main network.

Step 1: SIMATIC Shell for Server Communication

WinCC 7.5 has Remote Communication disabled by default. In SIMATIC Shell, enable:

• Terminal Bus (main network 192.168.0.x) — for clients and PLCs.
• Redundancy settings (backbone 10.10.10.x) — for heartbeat.

Assign IPs in Redundancy Editor and Shell. Servers recognized each other, and status displayed correctly.

Step 2: DCOM Setup in Workgroup

Launching Runtime threw the error RedundancyAgent: Initialization of Remote Communication failed. The issue: DCOM in workgroup mode needs manual authentication setup without a domain.

2.1. Services Under Administrator

Change the account for CCRedundancyAgent-Service:

• Open services.msc.
• Log On → This account → .\Administrator (identical passwords on both servers).

LocalSystem lacks network identity for DCOM.

2.2. DCOM Permissions

dcomcnfg → Component Services → My Computer → Properties:

COM Security → Access Permissions (Limits & Default):

• Everyone: Local/Remote Access Allow.
• ANONYMOUS LOGON: Local/Remote Access Allow.

Launch and Activation Permissions (Limits):

• Administrators: all Allow.
• Everyone: all Allow.
• ANONYMOUS LOGON: all Allow.

Launch and Activation (Default):

• SYSTEM, Administrators, Administrator: all Allow.

ANONYMOUS LOGON is required to initiate connections, followed by account verification.

2.3. Default Properties

• Enable Distributed COM: ✓
• Default Authentication Level: Connect.
• Default Impersonation Level: Identify.

2.4. LocalAccountTokenFilterPolicy

UAC filters the local Administrator token. Disable it:

New-ItemProperty -Path "HKLM:\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System" `
    -Name "LocalAccountTokenFilterPolicy" -Value 1 -PropertyType DWORD -Force

Restart WinCC Runtime.

2.5. Hosts File for Name Resolution

DCOM relies on NetBIOS names. Add to C:\\Windows\\System32\\drivers\\etc\\hosts on both servers:

10.10.10.1 SCADASERVER1
10.10.10.2 SCADASERVER2
192.168.0.1 SCADASERVER1
192.168.0.2 SCADASERVER2

Disable NetBIOS over TCP/IP on main network adapters (keep enabled on backbone).

Step 3: WinCC Redundancy Editor

Create the redundancy project:

• New project on Server1.
• Redundancy Editor → Add Server → specify SCADASERVER2.
• Connection Parameters: heartbeat timeout 5s, switchover delay 10s.
• Sync Runtime on Server2 (Server1 as primary).

Tags, archives, and scripts replicate automatically. Verify status: Master/Standby.

Step 4: Client Configuration

On SCADACLIENT0:

• Install WinCC Runtime Advanced.
• Add both servers to the project.
• Runtime → Automatic Server Selection: priority Server1, fallback Server2.

We tested failover: shutting down Server1 switched the client to Server2 in 15 seconds with no data loss.

Step 5: Production Deployment

After lab testing, we rolled it out to the plant. Backups before every change. Sync with live PLCs went smoothly. Monitor WinCC_Sys_XX.log logs closely.

Key Takeaways:

• In workgroup mode, DCOM is the bottleneck: 80% of time spent on permissions and tokens.
• Backbone is essential for heartbeat, not data.
• Hosts file + NetBIOS tweaks fix 90% of name resolution issues.
• Test failover in a lab with real PLCs.
• Apply all changes synchronously to both servers.

Total effort: 2 weeks in lab, 3 days in production. Migration cost beats domain setup.

— Editorial Team