Troubleshooting Redundant OS Server Download Failures: The Configured Server is Not Available

The error 'The configured server is not available' during OS project loading to a redundant standby server (OS_Stby / Server 2) or client in SIMATIC PCS 7 V7.1 SP2 indicates that the computer name in the transferred project does not match the actual Windows hostname or that Terminal Bus network communication is misconfigured. To resolve this, verify that the PC Station properties in SIMATIC Manager match the exact uppercase Windows NetBIOS hostname of Server 2, ensure the network share permissions allow write access from the ES user account, verify that the SIMATIC NET Terminal Bus adapter is set as the top priority network interface in Windows Network Bindings, and re-establish the redundant partner path in WinCC Explorer > Redundancy.

Executive Summary

High-availability Human-Machine Interface architectures in SIMATIC PCS 7 rely on redundant pairs of Operator Stations (OS Server 1 Master and OS Server 2 Standby) to ensure uninterrupted supervisory monitoring and historical archiving. During project commissioning or after an engineering station download, engineers frequently encounter a failure where OS Server 1 loads successfully, but attempting to load OS Server 2 (Standby) or an OS Client fails with error dialogs citing The configured server is not available or transfer aborts in LOAD.LOG. This condition severs server redundancy, leaving the standby node uninitialized. This problem stems from host name mismatches, improper Windows network binding orders, locked database shares, or stale redundant partner paths. This guide provides the complete procedure to restore redundant server downloads.

Redundant OS Server Architecture and Download Mechanics

When an engineer downloads an OS project from SIMATIC Manager (PLC > Download):

The ES connects across the Terminal Bus to the target station's administrative share (\\<ServerName>\<ShareName>).
It transfers the project database (<Project>.mdf), pictures (.pdl), scripts, and configuration tables.
It invokes WinCC Project Duplicator routines to update internal registry keys, replacing the master station's name with the standby server's computer name.
If the target machine cannot be reached via its declared NetBIOS name, or if Windows authentication fails, the download fails before database adaptation completes.

Root Causes for 'The Configured Server is Not Available'

Three primary engineering errors trigger this failure:

Host Name Mismatch: The computer name specified in the SIMATIC Manager PC Station properties differs (even by case or trailing space) from the actual Windows hostname configured under Windows System Properties.
Terminal Bus Binding Order: If the PC station has multiple Network Interface Cards (NICs) and the plant Terminal Bus is not listed first in Windows Network Adapter Provider Order, RPC calls bind to the wrong subnet.
WinCC Redundancy Configuration Desynchronization: If the partner server name in WinCC Explorer > Redundancy is blank or invalid, WinCC refuses to start the standby project.

Terminal Bus Network Configuration and Adapter Priority

According to Siemens manual 'Requirements for Operating SIMATIC WinCC in a Windows Network' (SIOS Entry 868014):

All OS Servers, Clients, and ES stations must reside in the same Windows workgroup or Active Directory domain.
The network protocol Simatic Device Drivers must be enabled on the Terminal Bus NIC.
In Windows Advanced Network Settings, the Terminal Bus network adapter must be positioned at the top of the connection list.

Redundant Server Diagnostic Matrix and Error Signatures

The following table compares download failure states, diagnostic indicators, and corrective actions:

Error Message / Dialog SymptomUnderlying Root CauseVerification File / ToolCorrective Engineering ActionThe configured server is not availableStandby computer name mismatch or invalid network share.LOAD.LOG on target serverAlign PC Station name with Windows hostname.Network path not found during downloadWindows Firewall blocking File Sharing (Port 445).Windows Command Prompt (ping -a)Open Windows Firewall ports 135, 137, 139, 445.Redundancy error: Partner not reachableTerminal Bus adapter binding order incorrect.Windows Network ConnectionsMove Terminal Bus NIC to top of provider order.Client download fails with LAD.LOAD errorClient PC station name does not match project entry.Client Project PropertiesRe-select target computer path in SIMATIC Manager.Project cannot be opened: Database lockedStale SQL lock file (*.ldf / *.mdf) in target folder.Target project folderDelete stale lock files or restart target server.

Step-by-Step Restoration and Project Download Procedure

Method 1: Verifying Hostnames and Windows Network Bindings

On OS Server 2 (Standby), open Command Prompt and run hostname. Note the exact uppercase name (e.g. OS_SRV02).
On the ES, open SIMATIC Manager. Right-click the PC Station for Server 2 and select Object Properties.
Confirm that the Computer name field exactly matches OS_SRV02.
On both OS Server 1 and Server 2, open Network Connections > Advanced > Advanced Settings.
In the Adapters and Bindings tab, ensure the network card assigned to the Terminal Bus is at the very top of the list.
Test network resolution from the ES by executing ping -a OS_SRV02 in Command Prompt.

Method 2: Configuring WinCC Redundancy and Executing Download

On the ES, open the master OS project (OS_SRV01) in WinCC Explorer.
Double-click the Redundancy editor in the navigation pane.
Confirm that Server: is set to OS_SRV01 and Redundant Partner Server: is set to OS_SRV02.
Check the box Activate Redundancy and configure the optional serial/Ethernet connection for connection checking.
Save and close WinCC Explorer.
In SIMATIC Manager, select the standby OS object (OS_Stby), right-click, and choose PLC > Download.
Select scope Entire project and execute. Monitor the progress bar to completion.

Verification

To verify that redundant server synchronization is fully operational:

Runtime Activation: Activate WinCC Runtime on OS Server 1, then on OS Server 2.
Redundancy State Inspection: In WinCC Explorer on Server 1, double-click the Redundancy icon in the Windows taskbar tray. Confirm that the status displays 'Master: In Runtime' and 'Partner: In Runtime' with redundancy active.
Client Failover Test: Open a process picture on OS Client 3. Disconnect the Terminal Bus cable from Server 1. Confirm that Client 3 switches seamlessly to Server 2 without operator interruption.

Limitations and Operational Precautions

Simultaneous Downloads Prohibited: Never initiate simultaneous downloads to both redundant servers. Always complete the download to Server 1 before downloading Server 2.
Identical Hardware Time Synchronization: Both redundant OS servers must be synchronized to a central NTP time master (such as SICLOCK or SCALANCE) to prevent archive synchronization conflicts.
Operating System Parity: Redundant server pairs must run identical Windows operating systems, service packs, and PCS 7 updates.

Engineer FAQ

Can I use Project Duplicator to copy the project to Server 2 instead of SIMATIC Manager?

While Project Duplicator works for standalone WinCC, in SIMATIC PCS 7, always use 'PLC > Download' from SIMATIC Manager to ensure multiproject station attributes are preserved.

What is the function of the redundant connection check cable between servers?

It provides an independent physical heartbeat line (serial RS232 or secondary Ethernet link) to prevent 'split-brain' scenarios if the Terminal Bus switch fails.

Where can I find the download error log file on the target computer?

The log file is created in the root of the target project directory and is named LOAD.LOG.

Technical References

Related Tags

https://industrialautomation.net/search?query=simatic-pcs7
https://industrialautomation.net/search?query=wincc-scada
https://industrialautomation.net/search?query=redundancy
https://industrialautomation.net/search?query=terminal-bus

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Troubleshooting Redundant OS Server Download Failures: The Configured Server is Not Available