Resolving Error 15124 During OS Compile After Renaming an S7 CPU in PCS 7

In SIMATIC PCS 7 (V9.0 SP2 / SP3), renaming an S7 CPU in SIMATIC Manager Component View that was previously compiled to WinCC triggers compilation aborts with Error 15124 ('Internal error: Compilation of process variables aborted'). This failure is caused by orphaned database pointers and desynchronized tag dictionaries between the Step 7 project database and the WinCC CS database. To resolve this, perform a slow project reorganization ('File > Save As... > with Reorganization (slow)'), delete cached compilation files (.asl and .dcf) in the OS project folder, and re-map and recompile the OS with memory reset enabled.

Executive Summary

During plant commissioning or system restructuring in SIMATIC PCS 7 V9.0 SP2 / SP3, automation engineers may need to rename an automation station (e.g., changing CPUA to CPUB in SIMATIC Manager Component View). While CFC charts compile without issues under the new station name, subsequent AS-OS compilations fail completely.

Both change compilations and full compilations abort with the fatal error message: Strukturierte Variable angelegt CPUB/@(4)/UR2ALU_1 *** Fehler ***: Interner Fehler: Das Übersetzen von Prozessvariablen wurde abgebrochen. Fehlernummer: 15124. Because the S7 CPU name forms the root prefix for WinCC communication channels, NetPro connections, and structured tag hierarchies, a simple text rename in Component View breaks relational foreign keys across the engineering database. This guide provides the complete recovery procedure to repair database references and eliminate Error 15124.

Architecture and Fundamental Mechanics

The AS-OS compilation engine (s7tgtopx.exe) links the Step 7 Sybase/SQL database to the WinCC Microsoft SQL Server database:

Role of the CPU Name in Tag Generation:
- Every process variable and structured tag compiled to WinCC incorporates the controller name: e.g., <CPU_Name>/<Chart_Name>/<Block_Name>.<Parameter>.
- In WinCC Tag Management, the communication connection under the SIMATIC S7 Protocol Suite is directly bound to the S7 CPU object name configured in NetPro.
The Renaming Discrepancy:
- When an engineer renames the CPU object in Component View, Step 7 updates the top-level container name, but internal cross-reference tables, AS-OS connection caches (*.asl), and WinCC configuration tables (CC_External_...) continue referencing the obsolete CPU name.
- When the AS-OS compiler runs, it detects that tags belonging to the old CPU name still occupy database slots in the WinCC CS database, while the new CPU attempts to create duplicate structured variables (such as @(4)/UR2ALU_1 system blocks).
- Unable to reconcile the conflicting station identifiers, the compilation engine terminates with Fehlernummer: 15124.
The Reorganization and Memory Reset Mechanism:
- Resolving Error 15124 requires clearing both the Step 7 database fragmentation and the WinCC tag dictionary cache:
- 'Save As... with Reorganization (slow)' sweeps the Step 7 database, recalculating internal object IDs and removing orphaned connection stubs.
- Deleting *.asl and .dcf files forces the compiler to purge stale tag mappings.
- In the AS-OS Compile Wizard, selecting 'With memory reset' (Urlöschen) clears the OS tag table, allowing the compiler to rebuild the connection and tag hierarchy cleanly under the new CPU name.

Step-by-Step Implementation Procedure

Follow these steps to recover from Error 15124 and recompile the OS successfully:

Archive Existing Multiproject:
- In SIMATIC Manager, select 'File > Archive...'.
- Generate a complete zip archive of the multiproject to establish a secure recovery point before making database modifications.
Reorganize Project Database:
- Select 'File > Save As...'.
- In the 'Save As' dialog, select the radio button 'with Reorganization (slow)'.
- Specify a new project storage directory and click 'OK'.
- Allow Step 7 to complete the comprehensive database sweep. This process eliminates orphaned records and rebuilds foreign key relational indices.
Purge OS Temporary Compilation and Connection Caches:
- Close SIMATIC Manager and WinCC Explorer.
- Open Windows File Explorer and navigate to the WinCC project directory inside the OS folder (e.g., <ProjectPath>\wincproj\<OS_Name>\).
- Locate and delete any files with the extension *.asl (AS connection list cache) and .dcf (Data Configuration File cache, e.g., <OS_Name>.dcf).
Re-verify NetPro S7 Connections:
- Reopen the reorganized multiproject in SIMATIC Manager.
- Open NetPro ('Options > Configure Network').
- Select the WinCC Application inside the PC Station.
- In the connection table, confirm that the named S7 connection points to the renamed CPU (CPUB).
- Execute 'Network > Save and Compile > Compile and check everything'. Ensure zero errors are reported.
Execute Full AS-OS Compile with Memory Reset:
- In SIMATIC Manager Component View, right-click the OS project object and select 'Compile'.
- Progress through the wizard to the screen 'Select the data you want to compile and the compile mode'.
- Select the radio button 'Entire OS' (not 'Changes only').
- Crucially, check the box 'With memory reset' (Urlöschen).
- Click 'Compile'. The compiler clears legacy tag definitions and regenerates all structured tags and connections under the new CPU name.

Verification

Inspect the AS-OS compilation output window: confirm that the compilation completes with 0 Errors, 0 Warnings and Error 15124 is not raised.
Open the WinCC project in WinCC Explorer: open Tag Management > SIMATIC S7 Protocol Suite > Named Connections.
Confirm that the connection reflects the new CPU name and that all process tags and system variables (@(4)/UR2ALU_1) are populated under the updated station prefix.
Start WinCC Runtime: verify that the named connection transitions to green (established) and live process data updates reliably.

Limitations and Operational Precautions

Compiling an OS 'With memory reset' purges all runtime tag definitions, historical trend configurations, and local alarm logging caches within the WinCC CS database. Always ensure a full project archive is created before performing a reorganization and memory reset. If external OPC servers, MES layers, or third-party SCADA systems query WinCC via exact CPU tag paths, their configuration mappings must be updated to match the new CPU name. Hardware expansions and licensing requirements should be verified through an authorized Siemens distributor or the Siemens Industry Mall.

Engineer FAQ

What causes Error 15124 during AS-OS compilation?

It occurs when internal database references between Step 7 and WinCC desynchronize after renaming a CPU, causing conflicting structured tag assignments in the WinCC CS database.

Does 'Save As with Reorganization (slow)' solve the problem alone?

Reorganization cleans the Step 7 database, but deleting cached *.asl and .dcf files and compiling 'With memory reset' in WinCC is required to completely clear stale tags.

Can a CPU be renamed online during plant operation?

No. Renaming an S7 CPU requires modifying NetPro named connections, re-compiling CFC charts and the OS, and downloading changes, which may require a controller restart.