Resolving WinCC OS Server Startup Failures and License Database Corruption After Low Disk Space Events

When a SIMATIC PCS 7 OS Server runs out of disk space on its project or logging volume (often partition D), Microsoft SQL Server and the Automation License Manager (ALM) frequently suffer database corruption, preventing WinCC Runtime from starting. Freeing disk space alone is insufficient because SQL transaction logs may be marked SUSPECT and ALM's local service database reports 'momentarily out of service' with licenses flagged as defective. To recover, terminate all hanging WinCC processes using Reset_WinCC.vbs, restart the SQL Server (WINCC) and Automation License Manager services, verify database file integrity, and re-validate licenses in ALM. Once database consistency is restored, download the OS project from the Engineering Station.

Cascading Failures Triggered by Low Disk Space on OS Servers

In a SIMATIC PCS 7 redundant Operator Station (OS) architecture, OS Servers continuously write real-time process data, cyclic Tag Logging segments, Alarm Logging messages, and audit trail records to Microsoft SQL Server databases hosted on secondary storage partitions (commonly drive D:). If partition D: exhausts all available free storage, active write transactions stall abruptly, causing severe cascading failures across multiple operating system and SCADA subsystems.

When free disk space reaches zero bytes, Microsoft SQL Server cannot expand transaction log files (.ldf) or commit active circular archive segments. The database engine forcibly switches databases to RECOVERY PENDING or SUSPECT mode. Simultaneously, the Automation License Manager (almsrvx.exe) service fails to record license verification transactions, causing the service to drop into fallback emergency logging and flag valid license keys as 'defective'. Simply moving or deleting archive files frees physical space but leaves WinCC internal lock files (ProjectOpened.lck, .dcf) and SQL catalogs in an orphaned, inconsistent state that prevents WinCC Runtime from launching.

Diagnostic Analysis of WinCC Runtime Lock and ALM License Corruption

Understanding the exact diagnostic messages generated during disk exhaustion is critical for targeted recovery:

Diagnostic MessageAffected ComponentUnderlying Root CauseOperational ImpactThe logging in the database on computer SVR1 is momentarily out of serviceAutomation License ManagerALM internal SQLite/SQL logging database failed due to disk write exhaustionALM logs transactions to a flat text file and blocks license validationLicense Key DefectiveAutomation License ManagerCluster/header record check failed on the hidden AX NF ZZ license storeRuntime packages cannot verify license authorization and abort startupServer started locallyWinCC OS Project ManagerOrphaned background process (CCProjectMgr.exe) holding project lockOS download from Engineering Station is rejected to prevent conflictAn error occurred while downloading to target stationSIMATIC Manager AS-OS EngineeringTarget database files are locked by crashed SQL processes or autostart loopProject download aborts, leaving target station in partial configuration

When Autostart is active on a corrupted OS Server, Windows continuously attempts to start AutoStartRT.exe, spawning hanging WinCC processes that continuously lock project files and prevent clean engineering downloads.

Step-by-Step Restoration Procedure for WinCC and ALM Databases

To recover a compromised OS Server and restore clean WinCC runtime operation, execute the following technical procedure:

Disable WinCC Autostart: Open Windows Start Menu -> Siemens Automation -> AutoStart. Remove the configured project path or uncheck Autostart to prevent automatic restart attempts during maintenance.
Terminate Hanging WinCC Processes: Open Windows Command Prompt as Administrator. Navigate to the WinCC binary directory and execute the termination script:

cd "C:\Program Files (x86)\Siemens\WinCC\bin"
Reset_WinCC.vbs

Wait until the script displays Reset_WinCC finished successfully. Verify in Windows Task Manager that processes such as CCProjectMgr.exe, CCDmRuntime.exe, SCRIPT.EXE, and WinCCExplorer.exe are completely terminated.

Run File System Check: Open administrative command prompt and execute chkdsk D: /f. Resolve any corrupted file allocation chains or invalid free space records caused by unexpected power disruptions or disk exhaustion.
Restart Core Services: Open Windows Services (services.msc). Restart the Automation License Manager Service and SQL Server (WINCC). Ensure both services start cleanly in 'Running' status.
Validate and Repair License Keys: Launch the Automation License Manager. Select the local drive containing licenses. Highlight all installed license keys, right-click, and select Check. If keys remain flagged as defective, select License Key -> Restore. If file corruption permanently corrupted the authorization header, contact Siemens Technical Support with the license Certificate of License (CoL) to generate emergency replacement keys.
Purge Orphaned WinCC Lock Files: In Windows File Explorer, browse to the OS Server project directory on drive D:. Delete any existing ProjectOpened.lck file and remove temporary database cache files (<ProjectName>.dcf).
Perform OS Download from Engineering Station: On the PCS 7 Engineering Station, right-click the OS Server object in SIMATIC Manager and select PLC -> Download. Perform an Entire WinCC Project download. Once download completes, activate WinCC Runtime and verify redundancy pairing.

Verification

Confirm system restoration and licensing integrity through the following diagnostic steps:

ALM Health Verification: In Automation License Manager, verify that all license keys for WinCC Server, WinCC Redundancy, and Process Objects show a green checkmark with status OK and zero defective entries.
WinCC Runtime Activation: Activate WinCC Runtime. Confirm that the WinCC status bar progresses through Graphics Runtime, Alarm Logging Runtime, and Tag Logging Runtime without displaying database connection error dialogs.
Redundancy Synchronization: Open the WinCC redundant partner server. Monitor internal tags @RM_MASTER and @RM_SERVER_STATE. Confirm that one server assumes Master status (1) and the other assumes Standby (2), with archive synchronization executing cleanly across the Terminal Bus.

Limitations and Operational Precautions

Observe these critical technical and commercial guardrails when managing OS Server storage and licensing:

Never Manually Manipulate AX NF ZZ: The license storage folder AX NF ZZ is a hidden, system-protected folder on the root of the partition. Never attempt to edit, copy, or delete files inside this directory using Windows Explorer, as doing so permanently invalidates Siemens cryptographic license clusters.
Maintain Free Space Thresholds: Configure Tag Logging archive properties in WinCC Explorer to restrict total archive size to no more than 70% of partition capacity. Maintain a minimum of 20 GB to 50 GB free headroom on drive D: for SQL Server tempdb and daily transaction bursts.
Commercial Accuracy Notice: Software licenses, runtime Process Object (RT PO) capacities, and redundancy entitlements are governed by Siemens licensing terms. Recovering damaged licenses requires valid proof of purchase (Certificate of License). Always validate final license entitlements and part numbers against current Siemens industry catalogs and authorized distributor quotations.

Engineer FAQ

Why did moving Tag Logging files not immediately allow WinCC to start?

Moving archive files frees storage sectors, but Microsoft SQL Server does not automatically detach or remount corrupted transaction log files (.ldf). Furthermore, orphaned lock files (ProjectOpened.lck) and active Autostart processes keep the project database locked until Reset_WinCC.vbs terminates them.

Can defective licenses in ALM be repaired without contacting Siemens?

If the defect is caused by an incomplete registry pointer or temporary file system cluster lock, running ALM's internal 'Check' or 'Restore' function after running chkdsk will recover them. If the cryptographic signature was overwritten during disk failure, an official Siemens Support Request with proof of license is mandatory.