Resolving 'Message Type Not Available or Inconsistent' During Slow Reorganization in SIMATIC PCS 7

In SIMATIC PCS 7 systems, the error 'Message Type Not Available or Inconsistent' encountered during a 'Save As with reorganization (slow)' operation indicates that legacy or corrupted message instance structures exist within the project database. Commonly occurring after migrating older projects from PCS 7 v7.x to v8.x, this defect is typically caused by outdated Sequential Function Chart (SFC) objects that retain obsolete single-instance message definitions rather than standard dual-instance structures. Resolving the error requires isolating the defective SFC charts, recreating them in the modern environment, transferring the sequencer logic, and removing the legacy charts.

Step 7 Slow Reorganization and Message Database Architecture

The SIMATIC Manager command File > Save As... > With reorganization (slow) is an essential maintenance utility that cleans internal Step 7 database fragmentation, purges deleted record pointers, and rebuilds binary B-tree tables. During this deep database compaction, the reorganization engine parses every configured message instance across CFC charts, SFC sequencers, and block containers to ensure structural consistency with the installed message server libraries.

In modern PCS 7 versions (such as V8.1 and V8.2), message handling relies strictly on CPU-oriented message numbers (ALARM_8P / AR_ID). If the database contains obsolete message definitions originating from legacy PCS 7 releases (such as V6.x or V7.0), the reorganization utility fails to match the legacy message headers with the current system schema, halting the reorganization with the error: Message Type Not Available or Inconsistent.

Migration Discrepancies in Legacy SFC Message Instances

The primary root cause of this inconsistency lies in Sequential Function Charts (SFC):
- Modern SFC Message Structure: Standard SFC charts in PCS 7 V8.1 instantiate two distinct message instances within their internal block header (one for sequencer status/step monitoring and one for operator prompt/fault messaging).
- Legacy SFC Message Structure: Older SFC charts created in legacy versions frequently contained only one message instance or utilized outdated project-oriented message configuration templates.
- When an engineer updates block types in CFC, function blocks are updated cleanly. However, static SFC charts stored in chart folders are not automatically restructured by the CFC Block Clean-Up tool, leaving obsolete message definitions trapped inside the project.

Diagnostic Isolation Workflow for Inconsistent Objects

Because the error pop-up does not identify the specific corrupted block or chart, engineers must isolate the offending object methodically:

Create Clean Target Project: In SIMATIC Manager, create a new temporary project with a dummy AS station.
Copy Block Containers: Copy all block types from the source AS to the target AS and perform Options > Block Types > Clean Up....
Group-Copy Charts:
- Copy CFC charts in batches of 20 to the target project.
- Execute reorganization on the target. If successful, those charts are clean.
Isolate SFC Charts:
- Copy SFC charts individually or in small groups.
- When copying an inconsistent SFC, SIMATIC Manager immediately triggers the error: Inconsistent messages.
Inspect Message Instance Count: Open the properties dialog of the flagged SFC, navigate to the Messages tab, and observe the instance table. Corrupted SFCs will show 1 message instance instead of 2.

Step-by-Step Remediation and Sequencer Migration

Once the defective SFC charts have been identified:

Create a Fresh SFC: In the original AS project, insert a new, blank SFC chart (Insert > Technological Objects > SFC). This new chart automatically inherits the modern dual-instance message schema.
Transfer Sequencer Topologies:
- Open the old inconsistent SFC and the new SFC side-by-side in the SFC Editor.
- Copy the sequencer steps, transitions, and branch networks from the old SFC and paste them into the new SFC.
- Verify that step actions, time parameters, and transition interconnections transfer cleanly.
Reassign Runtime Groups: In the Runtime Editor, assign the new SFC to the identical cyclic interrupt organization block (e.g., OB35) and execution position.
Delete Corrupted SFC: Delete the obsolete SFC chart from the chart folder.
Re-run Reorganization: Select File > Save As... > With reorganization (slow). The database reorganization will complete successfully with zero errors.

Migration and Reorganization Diagnostic Matrix

The following table details diagnostic symptoms and corrective paths during PCS 7 project reorganization:

Reorganization ErrorTypical Root CauseLocation of FaultCorrective Engineering Action'Message Type Not Available'Obsolete single-instance message templateLegacy SFC charts from V6/V7Recreate SFC in modern editor; copy sequencers; delete old SFC'Block type inconsistent'Modified FB interface not propagatedCFC block instancesExecute CFC > Options > Block Types > Update across multiproject'Cross-reference error'Corrupted reference databaseS7 Reference DataSelect Options > Reference Data > Generate to rebuild tables'Insufficient Memory'Project too large for 32-bit heapEntire MultiprojectReorganize individual AS projects separately

Note: Achieving a clean, error-free slow reorganization is mandatory prior to final customer handover and plant commissioning.

Verification

Verify project integrity after SFC remediation:
1. Open SIMATIC Manager and execute File > Save As....
2. Select target directory, assign a new project name, and check With reorganization (slow).
3. Monitor progress bar; verify the operation reaches 100% and closes without generating error dialogs.
4. Open the newly reorganized project; verify all CFC and SFC charts open cleanly.
5. Execute PLC > Compile > Entire Program; confirm compilation completes with 0 errors.

Limitations and Operational Precautions

Essential precautions when remediating legacy SFCs:
- Copying sequencer steps between SFCs transfers step actions, but WinCC block icon linkages and Plant Hierarchy assignments must be re-verified in Plant View.
- Always retain an untouched archive backup of the original migrated project prior to deleting any SFC objects.
- Ensure that the SFC execution order in runtime groups is preserved exactly to prevent unexpected sequence execution delays.

Engineer FAQ

Why did the CFC Block Clean-Up not fix the SFC message error?

The CFC Block Types clean-up tool updates function block prototypes (FBs), but it does not re-template internal message structures inside pre-existing standalone SFC chart instances.

Can I just ignore this error if the plant runs fine?

No. An inconsistent message structure will eventually cause fatal errors during OS compilation, prevent changes-only downloads, or trigger memory corruption during version comparisons in Version Cross Manager.