Resolving Computer Name and Connection Mismatches in PCS 7 OS Engineering Tools

In SIMATIC PCS 7, errors opening or compiling the Operator Station using the OS Engineering tools (WinCC Explorer, OS Compile, Database Automation) occur when the computer name registered in the WinCC project database (CC_<Project>.mdf) does not match the actual physical Windows computer name, or when the active network adapter assigned in Simatic Shell is disconnected. To resolve this, update the local computer name in WinCC Explorer properties, execute the Siemens Project Duplicator or CCChangeComputerName.exe utility, and verify that Simatic Shell binds to the active Terminal Bus adapter.

WinCC Project Registration and Computer Name Architecture

In SIMATIC PCS 7 multi-station architectures, the Operator Station (OS) environment relies on Microsoft SQL Server to manage project configuration and runtime data. When a WinCC project is created or compiled from SIMATIC Manager, the engineering database writes the specific NetBIOS computer name of the target PC into internal relational tables:
* In the project database file (<OS_Name>.mdf), the table CC_Computer records the authorized hostname (e.g. OS_SRV01).
* Internal server packages, communication channels, and WinCC Redundancy monitors reference this exact string.

If an OS project is copied to an engineering laptop, cloned onto a new server, or if Windows was reinstalled with a different hostname, the WinCC database engine detects a mismatch between the current Windows environment (%COMPUTERNAME%) and the database catalog. When an engineer attempts to open WinCC Explorer or execute an OS Compilation, the OS Engineering tool aborts with:
Error in OS-Engineering tool: The configured server is not available or computer name is invalid.

Root Causes for OS Engineering Tool Connection Errors

Three distinct system misconfigurations trigger this failure:
1. Host Computer Name Discrepancy:
The Windows computer name was changed after project creation, or a project retrieved from another plant was opened without updating the computer properties.
2. Disconnected or Misconfigured Simatic Shell Adapter:
WinCC uses the proprietary Simatic Shell service to discover and authenticate network stations across the Terminal Bus. If Simatic Shell is bound to an inactive virtual adapter (e.g. VMware host-only adapter) or a disconnected secondary port, WinCC cannot validate local IPC communication handles.
3. SQL Server Instance Security Locks:
If the local Windows user does not belong to the mandatory local security groups SIMATIC HMI and SQLServer2005MSSQLUser$..., the OS engineering tool is denied read/write permissions to the local database file.

The Critical Role of Simatic Shell on the Terminal Bus

Simatic Shell is the core communications broker for WinCC multi-user environments:
* It operates as a shell namespace extension in Windows Explorer (This PC -> Simatic Shell).
* It periodically broadcasts encrypted UDP multicast telegrams across the Terminal Bus to establish station discovery, server-client handshakes, and redundancy heartbeats.
* If multiple network interface cards exist on the PC (e.g. Terminal Bus NIC, Plant Bus CP 1623, and internal virtual adapters), Simatic Shell must be explicitly assigned to the Terminal Bus network card. If it binds to the Plant Bus or a disabled adapter, OS engineering utilities fail to communicate with local WinCC runtime processes.

Computer Name Migration and Diagnostic Matrix

The following matrix outlines tools and procedures for resolving computer name conflicts:

Diagnostic Tool / UtilityExecution EnvironmentFunction / ScopeRisk LevelWinCC Explorer GUI PropertiesProject already openRenames local computer objectZero (Standard Method)CCChangeComputerName.exeWindows command promptUpdates SQL table when project won't openVery Low (Automated tool)WinCC Project DuplicatorWinCC Explorer ToolsClones project with automatic name adaptationZero (Creates clean clone)Simatic Shell SettingsWindows Explorer ShellSelects active Terminal Bus network adapterZero (Network routing fix)Direct SQL Modification (SSMS)SQL Management StudioManual update of CC_Computer tableHigh (Risk of DB corruption)

Step-by-Step Procedure to Synchronize WinCC Computer Name

Follow this procedure to resolve connection errors and align computer names:
1. Identify the Exact Physical Computer Name:
- Open Windows Command Prompt (cmd.exe).
- Type hostname and press Enter. Note the exact case-sensitive string (e.g. ENG-STATION-01).
2. Verify Simatic Shell Binding:
- Open Windows File Explorer. Click This PC and select Simatic Shell.
- Right-click Simatic Shell and select Settings....
- In the network adapter dropdown, select the physical Ethernet card connected to the active Terminal Bus.
- If encrypted communication is enabled in your PCS 7 release, verify that the PSK key matches all other stations. Click OK.
3. Execute CCChangeComputerName (If Project Won't Open):
- Close all Siemens software.
- Navigate to the WinCC installation directory:
C:\Program Files (x86)\Siemens\WinCC\bin\
- Run CCChangeComputerName.exe.
- Point the tool to the target <ProjectName>.mcp file.
- Enter the new computer name (ENG-STATION-01) and click Apply. The utility automatically updates all internal SQL tables.
4. Update Computer Name in SIMATIC Manager:
- Open SIMATIC Manager. Open the Multiproject.
- Select the OS PC Station. Right-click and open Object Properties.
- Under the Computer Name field, enter ENG-STATION-01.
- In Component View, expand the PC Station -> WinCC Application. Open the WinCC project.
- In WinCC Explorer, expand Computer. Double-click the computer icon and verify the name reflects ENG-STATION-01.
5. Recompile the OS:
- In SIMATIC Manager, right-click the OS project and select Compile.
- Confirm that the OS compilation completes with zero connection errors.

Verification

Verify that OS Engineering tools function cleanly:
1. Open WinCC Explorer: Confirm the project loads immediately without displaying 'Server not available' error popups.
2. In WinCC Explorer, check the title bar: Verify it displays <ProjectName>.mcp - WinCC Explorer - [ENG-STATION-01].
3. In SIMATIC Manager, execute Compile OS: Confirm the compilation proceeds through tag generation, message generation, and SFC/BCC mapping without errors.
4. In Windows Explorer -> Simatic Shell: Confirm that local and remote PC stations appear in the list with blue running icons.

Limitations and Operational Precautions

Never rename a Windows computer while WinCC Runtime is actively running; doing so corrupts active SQL transaction logs.
In a redundant OS Server pair, the computer names of Server A and Server B must be completely unique and match their NetPro hardware configurations exactly.
Windows computer names must not exceed 15 characters and must not contain special characters (such as underscores _ or umlauts) to comply with NetBIOS and Siemens networking rules.

Engineer FAQ

Why does WinCC strictly enforce the computer name in the database?

WinCC uses distributed SQL database replication across server-client pairs. The computer name serves as the primary relational key identifying the origin of process data, alarm logging messages, and user control actions.

Can I rename my Engineering Station without reinstalling PCS 7?

Yes. After renaming the Windows computer and rebooting, update the Computer Name field in the SIMATIC Manager PC Station properties and execute CCChangeComputerName.exe on all associated OS projects.

What causes the error 'WinCC cannot connect to local SQL Server'?

This occurs if the Microsoft SQL Server service (MSSQL$WINCC) is stopped, or if the current Windows user was removed from the local SIMATIC HMI Windows user group.