Consequences of Duplicate Computer Names on OS Client and Server Stations in SIMATIC PCS 7

In SIMATIC PCS 7, operating an OS Client and OS Server with identical Windows computer names is strictly impossible, and attempting to resolve the conflict by renaming one PC after PCS 7 V8.2 is already installed will permanently corrupt system databases. During software installation, Microsoft SQL Server instances (WINCC), Microsoft Message Queuing (MSMQ), SimaticShell, and internal security certificates are cryptographically bound to the local Windows Computer Name. Renaming an installed station causes SQL Server startup aborts, broken DCOM remote procedure calls, and project database lockups. The only supported resolution is to perform a clean operating system reinstallation on the conflicting machine, configure its permanent unique computer name before installing any software, and reinstall PCS 7 from scratch.

Why Duplicate Computer Names Crash PCS 7 Terminal Bus Networks

In a SIMATIC PCS 7 distributed control architecture, communication between OS Servers and OS Clients across the Terminal Bus relies on Microsoft Windows networking protocols (NetBIOS, DNS, RPC) and Siemens SimaticShell broadcast services. Operating two computers with identical hostnames (e.g. both named SIMATIC_PC) causes immediate, catastrophic network conflicts:

Network SubsystemBehavior Under Duplicate HostnamesOperational Impact on PCS 7NetBIOS / WINS ResolutionName collision error logged; Windows disables networkingOperating systems refuse to communicate across the Terminal BusSimaticShell ServiceBroadcast discovery encounters conflicting MAC addressesOS Client cannot browse or connect to OS Server project packagesDCOM / RPC AuthenticationSecurity token validation rejects duplicate machine credentialsRemote faceplate and graphic calls fail with Access Denied errorsWinCC RedundancyPartner server state checks cannot differentiate nodesServer switchover logic fails; system enters split-brain fault

Network collision prevents the OS Client from mounting the server database, leaving operator screens in permanent disconnection.

Underlying System Dependencies Bound to Windows Computer Name

Automation engineers unfamiliar with PCS 7 internal architecture often assume they can simply open Windows System Properties, change the computer name of the OS Client from SIMATIC_PC to OS_CLIENT_01, and reboot. However, in SIMATIC PCS 7, renaming an installed station is strictly prohibited by Siemens product specifications.

During the initial PCS 7 installation wizard, the computer name is permanently written into low-level infrastructure engines:

Microsoft SQL Server (WINCC Instance): SQL Server instances register the server name in internal metadata tables (sys.servers). Changing the Windows name causes an unresolvable mismatch between @@SERVERNAME and the Windows hostname, preventing WinCC database attachment.
Message Queuing (MSMQ): WinCC uses private message queues for alarm routing and client-server synchronization. MSMQ paths (ComputerName\Private$\...) become orphaned and inaccessible.
Siemens Security Certificates & User Groups: Local security groups (SIMATIC HMI, SIMATIC NET) and internal SSL/TLS certificates are issued specifically to the original hostname.

Step-by-Step Clean Recovery and Reinstallation Procedure

To resolve duplicate name conflicts and establish a reliable, fully supported OS Client/Server pairing, execute the following technical recovery workflow:

Isolate Conflicting Machine: Disconnect the secondary PC (OS Client) from the physical Terminal Bus network cable to prevent ongoing IP/NetBIOS collision with the active OS Server.
Format Primary Partition: Boot the secondary PC from certified Windows installation media (Windows 7 SP1 Ultimate 64-bit or Windows Server depending on release). Perform a complete format of drive C: to wipe all orphaned SQL instances and registry keys.
Assign Permanent Unique Computer Name: Immediately after Windows installation completes—and BEFORE installing any Siemens software—open Windows System Properties. Assign the permanent, unique computer name (e.g. OS_CLIENT_01). Reboot the PC to instantiate the name.
Configure Fixed IP Settings: Assign static IP addresses and subnet masks matching the Terminal Bus subnet. Ensure DNS and hosts files resolve the OS Server (OS_SERVER_01) and OS Client (OS_CLIENT_01) bidirectionally.
Install SIMATIC PCS 7 OS Client Package: Insert the official SIMATIC PCS 7 V8.2 DVD. Run setup and choose Package Installation -> OS Client. Setup binds all SQL Server client components and SimaticShell hooks to OS_CLIENT_01.
Configure SimaticShell and Download: Reconnect the network cable. Open SimaticShell, set the active network adapter, and verify that OS_SERVER_01 appears in the network tree. Download the OS Client project from the Engineering Station.

Verification

Verify system separation and client-server connectivity through these diagnostic checks:

SimaticShell Neighborhood Audit: On the OS Client, open Windows File Explorer -> This PC -> SimaticShell. Verify that both OS_SERVER_01 and OS_CLIENT_01 appear in the node tree with blue active icons and zero collision alerts.
Ping and Name Resolution Test: Open Command Prompt on the OS Client. Execute ping OS_SERVER_01 and verify sub-millisecond replies. On the OS Server, execute ping OS_CLIENT_01.
WinCC Client Runtime Activation: Launch the OS Client runtime. Confirm that process graphics load from the server, alarm banners populate with live alarms, and clicking motor faceplates executes without DCOM security errors.

Limitations and Operational Precautions

When establishing station naming conventions across a PCS 7 plant, observe these strict engineering rules:

Strict Naming Syntax Rules: Siemens computer names must not exceed 15 characters, must contain only uppercase letters (A–Z), numbers (0–9), and hyphens (-). Special characters, spaces, and underscores (_) are prohibited by RFC NetBIOS specifications and can cause SQL Server replication failures.
Never Use Clone Images Without Sysprep: Deploying cloned hard drive images (Ghost, Acronis) onto multiple PCs without running Microsoft Sysprep causes duplicate Computer Names and duplicate Security Identifiers (SIDs), triggering fatal network lockouts.
Engineering Station Hardware Configuration: The assigned Windows Computer Name must match the station name configured in SIMATIC Manager HW Config with 100% case-sensitive precision.

Engineer FAQ

Can I use the Siemens tool 'RenameComputer' instead of reinstalling?

Siemens does not support computer renaming tools for full PCS 7 installations. While partial scripts exist for standalone WinCC, PCS 7 AS-OS engineering links and MSMQ queues frequently suffer silent data corruption after renaming.

Why can Windows handle computer name changes, but PCS 7 cannot?

Standard Windows applications run as stateless processes. PCS 7 relies on Microsoft SQL Server instances, distributed COM (DCOM), and local security groups that bind cryptographic tokens directly to the machine hostname upon setup.

Can two OS Clients share the same computer name if they never run at the same time?

No. Operating two machines with the same hostname creates severe Active Directory and DNS cache poisoning on the corporate network, even if operated alternately.