Troubleshooting OS Compilation Freezes and Crash of WinCC Explorer in SIMATIC PCS 7

When initiating an OS compilation from SIMATIC Manager and the compilation progress window abruptly closes followed by SIMATIC Manager freezing or WinCC crashing, the root cause is typically database corruption within the WinCC project cache file (<ProjectName>.DCF), SQL Server database deadlocks, or exhausted disk space in the project directory. During an OS compile, AS-OS Engineering executes mass SQL transactions to synchronize tags, messages, and archives. To diagnose and resolve the failure, engineers must inspect TRANSFER.log in [Project_Dir]\wincproj\[OS_Name]\ and WinCC_Sys_01.log in C:\Program Files (x86)\Siemens\WinCC\Diagnose\. The standard resolution is to close all Siemens applications, delete the cached .DCF file in the WinCC project root, verify database growth permissions in Microsoft SQL Server Management Studio, and execute a clean 'Compile Entire OS with Memory Reset'.

AS-OS Engineering Compilation Architecture and Failure Mechanics

In SIMATIC PCS 7, the compilation of the Operator Station (OS) represents the primary engineering interface where controller logic is translated into human-machine visualization. The AS-OS Engineering compiler reads all Continuous Function Charts, extracts technological block attributes (S7_m_c, S7_alarm_ui), opens the WinCC Microsoft SQL Server database, and performs high-volume batch inserts into the WinCC configuration tables (CS_Project).

If the compiler encounters an unhandled exception—such as a locked database table, a truncated string attribute in a custom block, a corrupted graphics script in GraCS, or an inconsistent cached connection—the compilation process terminates abruptly without displaying an error dialog. The background process Transfer.exe crashes, leaving the SIMATIC Manager GUI waiting indefinitely in a thread deadlock (freezing the user interface).

Diagnostic Inspection: TRANSFER.log and WinCC System Traces

To pinpoint the precise block, tag, or database table that caused the compile crash, inspect the diagnostic files:

Diagnostic Log FilePhysical LocationKey Error Signatures to IdentifyTRANSFER.log[Project_Dir]\wincproj\[OS_Name]\TRANSFER.logLast executed block before crash; Error in SQL Command, Table lockedWinCC_Sys_01.logC:\Program Files (x86)\Siemens\WinCC\Diagnose\Database transaction aborted, Out of Memory, Connection brokenPMTool.logC:\Program Files (x86)\Siemens\WinCC\Diagnose\Project Manager transaction errors; DCF cache synchronization faultsWindows Event ViewerWindows Logs -> ApplicationCrash dumps for Transfer.exe, CCProjectMgr.exe, or sqlservr.exe

Reviewing the final entries in TRANSFER.log reveals whether the crash occurred during Tag Management transfer, Alarm Logging message compilation, Picture Tree generation, or SFC visualization extraction.

Step-by-Step Procedure to Clear DCF Locks and Restore Compilation

To resolve OS compilation lockups and restore engineering functionality, execute this proven workflow:

Terminate Hanging Background Processes: Open Windows Task Manager. End any hanging instances of Transfer.exe, CCProjectMgr.exe, pdlrt.exe, and s7tgtopx.exe.
Close All Engineering Applications: Close SIMATIC Manager, WinCC Explorer, and CFC Editor.
Delete Cached Database Configuration File (.DCF): Navigate to the WinCC OS project root folder ([Project]\wincproj\[OS_Name]\). Locate the file <ProjectName>.DCF and delete it. The .DCF is a temporary binary cache that WinCC automatically rebuilds from the master SQL Server .mdf database on its next launch.
Run Siemens Assessment Suite (SAS) if Crashes Persist: If deleting the DCF does not resolve the issue, execute the SIMATIC Assessment Suite (SAS) diagnostic tool to capture crash memory dumps and identify corrupted project DLLs.
Execute Full OS Recompilation with Memory Reset: Reopen SIMATIC Manager. Right-click the OS object, select Compile, choose Entire OS, check With memory reset, and select both Tags and messages and SFC visualization. This flushes the SQL tables completely and generates a clean OS project.

Verification

Verify OS compilation health and database consistency using these checks:

Compilation Log Review: In SIMATIC Manager, right-click the OS object and select Display compilation log. Verify that the log concludes with 0 Errors and that all tags, messages, and archives transferred successfully.
WinCC Explorer Launch: Open the OS project in WinCC Explorer. Confirm that Tag Management and Alarm Logging open immediately without displaying database attachment warnings.
Runtime Activation Test: Activate WinCC Runtime. Verify that process pictures render without script errors and online communication with the AS functions smoothly.

Limitations and Operational Precautions

When troubleshooting OS compilation failures, observe these operational safeguards:

Never Delete .MDF or .LDF Files: While deleting the temporary .DCF cache is safe, never manually delete or move the SQL Server database files (<ProjectName>.mdf / <ProjectName>.ldf); doing so permanently destroys the OS configuration.
Disk Space Allocation: Ensure the drive hosting the PCS 7 Multiproject has at least 15 GB of free disk space. SQL Server requires substantial temporary workspace during mass table re-indexing.
Antivirus Exclusions: Verify that corporate antivirus software excludes the PCS 7 project folder and SQL Server data directories from real-time file scanning, as active file locking by antivirus agents is a primary cause of TRANSFER.log crashes.

Engineer FAQ

Is it safe to delete the .DCF file?

Yes. The .DCF (Database Configuration File) is an operational cache file. When deleted, WinCC Explorer reads the master SQL Server .mdf database and automatically regenerates a clean, uncorrupted .DCF upon next opening.

Why does checking 'With memory reset' during OS compile help?

'With memory reset' instructs AS-OS Engineering to drop and recreate the temporary transfer tables in WinCC SQL Server, clearing out orphaned tags and incomplete transaction fragments left behind by previous crashed compiles.

What is the Siemens Assessment Suite (SAS)?

The Siemens Assessment Suite (formerly SIMATIC Assessment Suite / SAS) is an automated diagnostic collection tool provided by Siemens Technical Support to gather log files, crash dumps, and system event traces for rapid root-cause analysis.