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Resolving SFC Type Deletion Error 1739:20 in SIMATIC PCS 7 - Database Cleanup and CFC Update 3

Resolving SFC Type Deletion Error 1739:20 in SIMATIC PCS 7 - Database Cleanup and CFC Update 3

In SIMATIC PCS 7 (specifically v8.1 and v8.2 environments), attempting to delete an SFC Type from the Master Data Library or S7 program chart folder that aborts with error code '1739:20 - Step does not exist (any longer)' indicates database index corruption within the chart database (pbase.db). This condition occurs when an engineer attempts to delete an SFC Type while instances or chart references still linger, or when a known compiler defect leaves orphaned step/transition pointers in the internal project catalog. To resolve this error, engineers must install the official Siemens cumulative patch 'SIMATIC CFC V8.2 Update 3' (or newer), execute a project database reorganization in SIMATIC Manager, and clear orphaned block pointers.

Table of Contents

Deconstructing SFC Error 1739:20 and Internal Chart Databases

In SIMATIC PCS 7, Sequential Function Chart (SFC) Types are object-oriented templates defined within the Master Data Library. Unlike flat logic files, an SFC Type is tightly coupled to multiple relational database tables within the project's pbase.db and Sycon.db files:
- Topology Tables: Store the graphical layout of steps, transitions, and branches.
- Action Tables: Store low-level instruction pointers for initialization, processing, and termination phases.
- Instance Catalogs: Track all instantiated SFC instances across the plant hierarchy.

When an engineer selects an SFC Type and presses Delete, the engineering engine executes a recursive verification routine. If an internal database pointer points to a record ID whose corresponding step index is corrupted or missing, the deletion parser crashes with error message:
Note 1739:20 - Step does not exist (any longer).

Root Causes of Orphaned Step and Transition Pointers

Four specific failure mechanisms induce error 1739:20:

  1. Known CFC Compiler Defect (Resolved in Upd3): In the base releases of PCS 7 v8.2 and v8.2 Upd1/Upd2, a defect in the CFC chart manager failed to clean up internal step pointers when steps were deleted inside an SFC Type. Siemens officially resolved this bug in CFC V8.2 Update 3.
  2. Deleting Types Prior to Instance Removal: Attempting to delete the master SFC Type from the library while instantiated SFC charts still exist in the plant hierarchy breaks parent-child relational integrity. Even if the instances are subsequently deleted, the orphaned foreign keys remain in pbase.db.
  3. Aborted Copy/Move Operations: Moving SFC charts between projects while a multi-user session or background compilation was active can leave ghost records in the target folder.
  4. Manual Block Deletion in S7 Block Folder: Manually deleting the underlying FB generated by the SFC Type directly from the offline block folder (instead of using the SFC Editor) corrupts the chart-to-block synchronization table.

Software Patch Remediation: CFC V8.2 Update 3

Siemens published a comprehensive resolution specifically addressing Note 1739:20:
- Patch Package: SIMATIC CFC V8.2 Upd3 (Entry ID: 109743846).
- Core Fix: The patch updates the SFC compiler (sfc.exe) and chart manager (cfc.exe), introducing an automated database scrubbing routine that purges orphaned step and transition pointers during compilation.
- Backwards Compatibility: Once installed on the Engineering Station, opening the project automatically repairs the corrupted SFC Type catalog.

Step-by-Step Procedure: Repairing Project Databases and Deleting Types

Follow this procedure to eliminate the error and cleanly remove unwanted SFC Types:

Step 1: Install CFC V8.2 Update 3

  1. Close SIMATIC Manager and all engineering tools.
  2. Download and install CFC V8.2 Update 3 (or the latest cumulative CFC update from SIOS).
  3. Restart the Engineering Station.

Step 2: Ensure All Instances Are Deleted

  1. In SIMATIC Manager, open View > Process Object View.
  2. Switch to the SFC tab.
  3. Verify that zero instances of the target SFC Type exist across all AS stations. If any exist, delete them from the plant hierarchy.

Step 3: Execute Slow Project Reorganization

  1. In SIMATIC Manager, open the project containing the problematic SFC Type.
  2. Select File > 'Save As...'.
  3. Check the box 'With Reorganization (Slow)'.
  4. Choose a temporary project name (e.g., Project_Reorg).
  5. Click OK; this reconstructs internal database indices from scratch, purging orphaned records.

Step 4: Delete the SFC Type

  1. Open the reorganized project in SIMATIC Manager.
  2. Navigate to [S7 Program] > Charts.
  3. Select the problematic SFC Type, right-click and choose Delete.
  4. The SFC Type will delete cleanly without triggering Note 1739:20.

Diagnostic Matrix for SFC Type Management Errors

The table below outlines common SFC deletion and manipulation faults:

Error CodeError MessageUnderlying CauseRemediation Action1739:20Step does not exist (any longer)Orphaned step index in pbase.dbInstall CFC V8.2 Upd3; execute Save As with Reorganization1739:15SFC Type is still instantiatedInstances exist in plant hierarchyDelete all SFC instances before deleting type1739:35Block number conflict during compileUnderlying FB number already assignedReconfigure reserved FB range in CFC customize menu1739:02Cannot read chart databaseDatabase lock file activeClose all tools; delete temporary *.ldb / *.loc files

Verification

To confirm that the project database is repaired:
1. SFC Type Deletion Verification: Confirm that the target SFC Type is removed from the Charts folder without error dialogs.
2. Chart Consistency Check: In SIMATIC Manager, select the Charts folder and click Options > Charts > Check Consistency; verify that 0 errors and 0 warnings are logged.
3. Full AS Compilation: Execute Compile > Charts as Program > Entire program; verify that the S7 program compiles cleanly without missing block errors.

Limitations and Operational Precautions

Engineering teams must observe the following precautions:
- Always create a complete project backup archive (File > Archive...) before performing slow reorganization or deleting technological types.
- Never delete SFC-generated Function Blocks directly from the offline block folder; deletions must strictly be executed through the SFC/CFC chart interfaces.
- Always validate that all participating multi-user engineering laptops have the identical CFC update level installed to prevent re-introducing database corruption.

Engineer FAQ

Can I just empty the inside of the SFC Type instead of deleting it?

While deleting internal steps removes execution logic, the empty SFC Type still consumes an FB number and Process Object references. Installing CFC Upd3 and cleanly deleting the type is the proper engineering solution.

Does installing CFC V8.2 Update 3 require a CPU STOP?

No. CFC Update 3 is an engineering toolset update installed on the Engineering Station; it does not alter controller firmware or require stopping the AS controller.

Where can I download CFC V8.2 Update 3?

CFC updates are available free of charge to registered Siemens users on the Siemens Industry Online Support (SIOS) portal under Entry ID 109743846.

Technical References

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Related Tags

  • SFC Types
  • Error 1739:20
  • CFC Update 3
  • Database Corruption
  • Reorganization
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