Resolving WinCC Project Loading Errors: Network, SQL, and Login

WinCC projects fail to load for three recurring root causes: corrupted Windows network neighborhood state on legacy PCS 7 v5.x redundant servers, SQL Server connectivity loss in DataLogging/AlarmLogging, and user-management desynchronization on WinCC Unified V16-V18. This reference documents the field-verified fix for the v5.0 → v5.1 conversion case (417-H redundant server pair, three clients), the STEP 7 v5.2 SQL connection failure, and the Unified Runtime login fault referenced in Siemens KB 109805541 and the TIA Portal V20 RT Unified error catalog.

1. Problem Summary

Three distinct WinCC failure modes are documented below. Each is mapped to the product line, firmware/software version, and the verification step that confirms recovery.

2. Case A: Missing .pdl Files After v5.0 → v5.1 Project Conversion

2.1 Observed Behavior

After migrating a PCS 7 project from WinCC v5.0 to v5.1 on a redundant AS 417-H server pair (two redundant servers, three clients), the following appeared in the project:

• WinCC Explorer opened normally.
• Tag Management → S7 Protocol Suite → Industrial Ethernet showed the configured tags.
• Graphics Designer contained no .pdl files.
• Base Data refused to open.
• WinCC Runtime would not start.

Siemens regional support confirmed this signature was not in their standard issue database. The root cause was traced to the Windows NT network neighborhood state on the redundant pair, not to the WinCC project database itself.

2.2 Root Cause

WinCC v5.0 SP1 / SP2 (and the v5.1 upgrade path) imposes stringent rules on the configuration of the underlying Windows NT/2000 network connection of the WinCC station. The Industrial Software Hotline maintains the full rule set (obtainable through the general SIMATIC Support number). A common failure trigger is a stale or partial network neighborhood entry created by the upgrade installer when it promotes the redundant partner role — the upgrade writes the new WinCC project paths but leaves a reference to the old network binding, which WinCC then resolves against a phantom server and refuses to enumerate the picture tree.

2.3 Resolution Procedure

1. On the affected WinCC station (apply to both redundant servers in maintenance window), open Control Panel → Network.
2. Record the current bindings, services, and protocols so the rebuild matches the original configuration.
3. Delete the entire Network Neighborhood entry — services, protocols, adapters, and client bindings.
4. Reboot the station. Windows will enumerate the network stack fresh and request the protocols at first logon.
5. Rebuild Network Neighborhood from the recorded configuration, in the same protocol order. The Industrial Ethernet CP 1613 / CP 1623 driver must be bound before the standard Microsoft client.
6. Reboot a second time. Verify the redundant partner resolves by name in the S7 protocol suite diagnostic.
7. Open WinCC Explorer and confirm the .pdl files are present in Graphics Designer.
8. Open Base Data and verify it loads without error.
9. Start WinCC Runtime in simulation; confirm tag simulation toggles the configured I/O.
10. On the redundant partner, repeat steps 1–9 before re-enabling redundancy in the project.

2.4 Verification Checklist

3. Case B: SQL Server Connection Failure on STEP 7 v5.2 + WinCC

3.1 Observed Behavior

When STEP 7 is upgraded to v5.2 on a station that also hosts WinCC, the following appears:

• DataLogging runtime does not start; the process data archive remains empty.
• AlarmLogging runtime reports "Database connection failed."
• The SQL Server service appears started, but the WinCC alias WinCC cannot be resolved to a live instance.

3.2 Root Cause

STEP 7 v5.2 re-registers its own SQL client libraries in the Windows registry. The WinCC runtime uses a named-pipe alias called WinCC that points to the local MSSQLSERVER instance. When STEP 7 v5.2 overwrites the alias or the named-pipe protocol binding, the WinCC runtime cannot locate the instance and refuses to start DataLogging and AlarmLogging.

3.3 Resolution Procedure

1. Stop the WinCC Runtime and the WinCC DataMonitor / Connectivity services if running.
2. Open SQL Server Client Network Utility (cliconfg.exe) and verify the alias WinCC exists, points to the local server, and uses the named pipes protocol on pipe \\.\pipe\sql\query.
3. If the alias is missing or points to TCP only, recreate it: name WinCC, server (local), protocol named pipes, pipe name \\.\pipe\sql\query.
4. Open SQL Server Enterprise Manager, expand the local instance, and confirm the WinCC project database is attached and marked read/write.
5. Open the Windows service MSSQLSERVER, set startup to Automatic, and restart it.
6. Re-register the WinCC runtime libraries by running WinCC\bin\SFM.exe /regserver from the WinCC installation directory.
7. Start WinCC Runtime and confirm the green "Database connected" indicator appears in the DataLogging and AlarmLogging control dialogs.

3.4 Verification Checklist

4. Case C: WinCC Unified Runtime Login Failure (V16, V17, V18)

4.1 Observed Behavior

Per Siemens KB 109805541, login errors appear in WinCC Unified Runtime when:

• User management data is not synchronized with the runtime after a TIA Portal project change.
• The UmclService account does not have read permission for the SCADAProjects directory.
• The user was created in the TIA Portal project but the project was not reloaded to the runtime after the user change.

4.2 Root Cause

WinCC Unified stores user management data in a project-specific directory under C:\Program Files\Siemens\Automation\WinCCUnified\SCADAProjects. The UmclService Windows service reads this directory on each runtime start to build the in-memory user table. If the ACL on SCADAProjects is changed by an installer, an antivirus scan, or a Windows update, UmclService cannot read the user data and all login attempts are rejected with a generic "Login failed" or "UM not synchronized" error.

4.3 Resolution Procedure

1. Open Services and confirm Siemens UmclService is running and set to Automatic (Delayed Start).
2. Open File Explorer, navigate to C:\Program Files\Siemens\Automation\WinCCUnified\SCADAProjects.
3. Right-click the project folder → Properties → Security → Advanced.
4. Verify that the UmclService account (or the SYSTEM account if the service runs as LocalSystem) has Read & execute, List folder contents, and Read permissions. If missing, add the account and apply.
5. In TIA Portal, open the WinCC Unified device, expand User management, and click Synchronize with runtime.
6. Confirm the synchronization completes without error in the TIA Portal output window.
7. Restart the Unified Runtime from TIA Portal (Online → Runtime → Restart) or via the device web page.
8. Attempt login with a known user; the login dialog should close and the start page should render.

4.4 Verification Checklist

5. Unified RT Project Loading Errors (TIA Portal V20)

Per the TIA Portal V20 RT Unified error catalog, download failures from TIA Portal to a Unified Panel or PC runtime typically fall into the following categories:

6. Network Neighborhood Rules for WinCC v5.x

The Siemens Industrial Software Hotline publishes a binding rule set for WinCC v5.0 SP1 / SP2 stations. The most frequently violated rules are:

1. The TCP/IP protocol must be bound after the Industrial Ethernet CP driver (CP 1613, CP 1623, CP 1628).
2. Only one active network adapter may be bound to the Microsoft Client; additional adapters must be disabled or used solely for the S7 communication.
3. DNS resolution must be configured before NetBIOS; pure NetBIOS resolution is not supported in v5.1.
4. The redundant partner hostname must resolve in both directions (forward and reverse) before the WinCC project is started.
5. File and printer sharing must be enabled on the WinCC server for client picture transfer.

Failure to apply rule 1, 2, or 4 produces the symptom pattern documented in Case A above. The full rule set is available only through the hotline, not the install media.

7. Preventive Hardening Checklist

8. Diagnostic Command Reference

9. Escalation Path

1. Collect the WinCC version and service pack, the STEP 7 version, the OS version with service pack, and the error text from the WinCC diagnostic file (default: <project>\diagnose\<date>.txt).
2. Reproduce the failure on a single station with the redundant partner removed to isolate the issue.
3. If the failure persists after the resolution procedure above, contact the Siemens Industrial Software Hotline via the general SIMATIC Support number and reference KB 109805541 for Unified login issues, or the TIA Portal V20 error catalog for RT loading issues.