How to Resolve F-Tool Compilation Error 256:107 and File Access Crashes in PCS 7 Engineering Stations

In SIMATIC PCS 7 V8.1 SP1 with S7 F Systems, compilation crashes accompanied by F-Tool error 256:107 ('Unable to copy the object... not enough space, destination directory is blocked') and online SFC monitoring file access errors (dumping code 730 in DOTS00.log) stem from file-locking conflicts caused by active antivirus scanners, Windows indexing services, or corrupted temporary compile caches. To resolve this, configure strict antivirus exclusions for STEP 7 directories, purge locked temporary files (~TMP, DOTS.log, TDN), verify user administrative rights on the Engineering Station, and execute a 'Save As with Reorganization (Slow)' to rebuild the project database.

Anatomy of Engineering Station Compilation and File Access Crashes

In a SIMATIC PCS 7 engineering environment, compiling an automation program with fail-safe logic involves intense, multi-threaded disk operations:
* The standard CFC compiler generates user code, calculates execution groups, and builds instance data blocks.
* Simultaneously, S7 F Systems invokes the F-Tool safety compiler, which copies pre-compiled safety blocks (F_OR4, F_AND4, F_CH_DI) from S7 F Systems Lib into temporary working folders, executes CRC signature hashing, and generates fail-safe communication telegrams.
* Concurrently, online monitoring routines spawn temporary session tracking logs (such as DOTS00.log).
* If any background Windows process intercepts, scans, or locks these temporary directories during compilation, the compiler experiences access denial, triggering catastrophic crashes or corrupting the project symbol table.

Root Causes of F-Tool Error 256:107 and DOTS00.log File Access Faults

The specific compilation errors reported by engineers:
1. F-Tool Error 256:107:
* Message: Unable to copy the object S7 F System Lib/V1_3\F-Userblocks\symboles\F_OR4... not enough space, destination directory is blocked.
* Despite adequate physical hard drive space, this error occurs because the target compile directory contains locked temporary files from a previous crashed compile, or an antivirus process has placed a read-lock on the file while computing heuristic signatures.
2. SFC File Access Error (DOTS00.log Error 730):
* During online monitoring of Sequential Function Charts, the SFC runtime editor attempts to write debugging states into DOTS00.log.
* Error 730 indicates a low-level operating system file sharing violation (ERROR_SHARING_VIOLATION): another process has locked the log file with exclusive access.
3. Symbol Table Editing Crashes:
* Editing the symbol table while a background compilation is actively executing creates database deadlocks between the STEP 7 Sybase/SQL database engine and the table editor, corrupting the project index.

Isolating ES Build Corruption vs Project Database Damage

When persistent errors reappear despite multiple project reorganizations, determine whether the fault resides in the project files or the Engineering Station software installation:

The Test Multi-Project Benchmark:
1. In SIMATIC Manager, select File > 'New Project' Wizard.
2. Create a clean, minimal test multi-project with one AS CPU (configure an S7-400H or standard CPU) and one simple CFC chart containing basic channel drivers and one F-block (F_OR4).
3. Compile the test project: Chart > Compile > Entire Program.
Diagnostic Conclusion:
If the test project fails with identical errors: The Engineering Station installation is damaged. Antivirus policies, corrupted S7 F Systems binaries, or broken Windows permissions are blocking execution.
If the test project compiles cleanly: The Engineering Station is healthy. The original project database contains corrupted cross-reference pointers or orphaned file locks requiring a deep database purge.

Step-by-Step Recovery Procedure: Antivirus Exclusions and Cache Purging

To eliminate file-locking conflicts and restore reliable compilation:

Configure Mandatory Antivirus Exclusions:
* Add the following directory trees to corporate endpoint antivirus real-time scanning exclusions:
- C:\Program Files (x86)\SIEMENS\*
- C:\Program Files\SIEMENS\*
- The root folder containing all PCS 7 project data (e.g., D:\PCS7_Projects\*).
- Exclude file extensions: .s7p, .dbf, .mdf, .ldf, .tdn, .log.
Purge Locked Temporary Files:
* Close all SIMATIC software and reboot the Engineering Station to release all file handles.
* Open Windows Explorer and navigate to the project directory:
D:\PCS7_Projects\[Project_Name]\[AS_Name]\~tmp\
* Delete all temporary files (*.tdn, *.tmp, DOTS*.log).
Execute Deep Project Reorganization:
* Open SIMATIC Manager.
* Select File > 'Save As...'.
* Check the radio button: With Reorganization (Slow).
* Specify a new project destination folder and click OK.
* SIMATIC Manager defragments the database, strips orphaned handles, and rebuilds internal index tables cleanly.

Comparison of Compilation Error Symptoms and Corrective Measures

The table below outlines common PCS 7 compilation failure codes, root mechanisms, and verified solutions.

Error Code / MessageSubsystemRoot Failure MechanismCorrective ActionError 256:107S7 F Systems / F-ToolDestination directory locked by antivirus or crashed processAdd antivirus exclusions; purge ~tmp folderError 730 (DOTS00.log)SFC Runtime MonitorOS sharing violation on temporary debug logReboot ES; delete DOTS*.log from project folderSymbol Table CrashSTEP 7 DatabaseConcurrent write collision during background compileNever edit symbol table while compiling; run Save As SlowError 256:101F-ToolMissing or mismatched F-Configuration licenseVerify S7 F Systems license in ALM

Verification

To confirm that compilation integrity is fully restored:
1. Open SIMATIC Manager and open the newly reorganized multi-project.
2. Open a CFC chart containing fail-safe logic and select Chart > Compile > Entire Program.
3. Verify that the compilation dialog proceeds through F-Tool generation without pauses or error dialogs.
4. Confirm that the compilation log outputs: Compilation complete: 0 Error(s), 0 Warning(s).
5. Open an SFC chart online: verify that online monitoring activates immediately without generating DOTS00.log error popups.

Limitations and Operational Precautions

Never edit symbol tables, hardware configurations, or block interfaces while a CFC or OS compilation is actively underway; concurrent writes cause irrecoverable database corruption.
Do not disable antivirus protection entirely; instead, strictly implement Siemens-approved folder exclusions to maintain workstation cybersecurity.
When working with S7 F Systems, ensure the installed F-library version (e.g., S7 F Systems Lib V1_3) exactly matches the safety certification of your installed PCS 7 release.
Always archive a copy of the project before performing 'Save As with Reorganization (Slow)'.

Engineer FAQ

Why does F-Tool report 'not enough space' when my hard drive has 100 GB free?

The error string 'not enough space or destination directory is blocked' is a legacy Windows error translation. In reality, the folder is write-blocked because another process (such as antivirus scanning or a lingering crashed compilation process) has locked the directory handle, preventing F-Tool from copying temporary safety blocks.

What does the 'Save As with Reorganization (Slow)' actually do?

Standard 'Save' merely appends changes to existing database files. 'Save As with Reorganization (Slow)' creates a brand-new database from scratch, reading only verified valid records, purging orphaned pointers, defragmenting data tables, and eliminating residual file locks.

Can I delete the DOTS00.log file safely?

Yes. DOTS00.log is a temporary session debugging log generated during online SFC monitoring. Deleting it when SIMATIC Manager is closed is completely safe and clears locked file handles.