Resolving WinCC OS Compilation Error 1739:10 'Invalid Object Type' During Changes Compile in SIMATIC PCS 7

In SIMATIC PCS 7 projects migrated between service packs (such as PCS 7 v7.1 SP2 to SP4 or v8.0 to v8.2), the OS compilation error 'Invalid object type (1739:10)' during a changes compile occurs because the delta compilation cache in the ES project database contains obsolete OCM (Operator Communication and Monitoring) object references that do not match the updated library block headers. A changes compile attempts to resolve differential object IDs against cached cross-references. Executing a complete OS compilation ('Entire OS with Memory Reset') discards the corrupted delta cache, synchronizes all AS block instance structures with WinCC Tag Management, and completely eliminates error 1739:10.

Root Cause of Error 1739:10 During Delta OS Compilation

During the lifecycle of a SIMATIC PCS 7 automation plant, engineering stations are periodically upgraded across Service Packs (e.g. from PCS 7 v7.1 SP2 to v7.1 SP4, or PCS 7 v8.1 to v8.2). While the automation logic may execute without warning on the controller, compiling the operator station (OS) using the Changes compile option can trigger:

Error: Invalid object type. (1739:10)

This error originates from internal schema discrepancies within the STEP 7 project database (.dbf and .s7p tables):
1. Delta Compilation Mechanism:
- When an engineer selects Compile OS > Changes, the OS compiler (s7tosx.exe) interrogates the engineering database's internal modification logs.
- It compares previous compilation timestamps against changed CFC charts, SFC types, and block instances marked with the S7_m_c := 'true' attribute.
2. Obsolete Type Signatures:
- Upgrading PCS 7 or importing modified library blocks alters internal data type descriptors (UDTs), block interface signatures, and OCM object handles.
- If a project is archived on an older service pack and retrieved on a newer service pack, the delta compilation cache contains legacy pointers to object types that the newer compiler no longer recognizes, producing error 1739:10.

Differences Between Changes Compile and Complete OS Compilation

Understanding the behavioral difference between delta and full OS compilation is crucial for resolving database corruption:
- Compile Changes Only:
- Transfers only modified tags, alarms, and archive tags.
- Preserves runtime connectivity and permits online download of changes to redundant OS servers while plant operations continue uninterrupted.
- Relies strictly on the validity of previous compilation state tables.
- Entire OS (Complete Compilation):
- Completely bypasses the incremental cache.
- Re-reads every CFC chart, SFC chart, and HW Config station across the entire Multiproject from source files.
- Rebuilds WinCC Tag Management, Alarm Logging messages, and Tag Logging archives from scratch.
- Re-indexes all internal OCM object GUIDs and Clears obsolete delta state flags.
- While a complete compile requires an offline download to OS servers (or a controlled server switchover), it permanently purges corrupt incremental references.

Step-by-Step Resolution Workflow

To eliminate error 1739:10 and restore normal incremental compilation:

Perform Database Reorganization:
- In SIMATIC Manager, close all open CFC charts, SFC editors, and WinCC Explorer.
- Select File > 'Save As...'.
- Select With Reorganization (Slow).
- Save the project to a clean directory path. This eliminates dangling relational database keys.
Execute Block Type Cleanup in CFC:
- Open any CFC chart in SIMATIC Manager.
- In the menu, select Options > Block Types.
- Click Clean Up. This removes unused block types from the project chart container.
- Next, click Update Block Types to ensure all blocks in the charts match the installed PCS 7 library versions.
Execute Full OS Compilation:
- Right-click the OS project object in SIMATIC Manager and select Compile.
- In the compilation wizard, select Entire OS.
- Check the box With memory reset (if available in the installed PCS 7 version).
- Ensure the correct S7 programs and network connections are checked.
- Start compilation. The compiler completes without error 1739:10.
Re-establish Delta Baseline:
- After the successful complete compile, make a minor tag comment change in one CFC chart.
- Execute Compile OS > Changes.
- Verify that incremental compilation completes with zero errors, confirming the delta baseline is restored.

OS Compilation Mode Comparison and Troubleshooting Table

The following table compares OS compilation options and their impact on project consistency:

Compilation ModeCache UtilizationOnline Download SupportedResolves Error 1739:10Recommended Usage ScenarioChanges CompileReads delta cache tablesYes (Zero plant downtime)No (Fails if delta cache is corrupt)Routine day-to-day logic modificationsEntire OSBypasses delta cacheRequires OS restart / switchoverYes (Rebuilds all object pointers)After PCS 7 SP upgrades or block library importsEntire OS with Memory ResetPurges and recreates OS DBRequires complete OS downloadYes (Cleans orphaned WinCC internal tags)Resolving severe database mismatches or error 16003Save As with ReorganizationRebuilds STEP 7 databaseN/A (Offline ES operation)Prerequisite stepEliminating corrupted database records and file bloat

Verification

To confirm that error 1739:10 is completely resolved:
1. In SIMATIC Manager, select the OS station, right-click, and select Compile.
2. Select Entire OS and execute compilation. Confirm that the compilation log finishes with:
text Compilation completed: 0 errors, 0 warnings.
3. Open WinCC Explorer on the ES and check Tag Management. Verify that all AS structure tags, @PCS7 system variables, and message archives are fully populated.
4. Open a CFC chart, modify a non-critical parameter (e.g. an alarm high limit), and save the chart.
5. Select Compile OS > Changes. Confirm that incremental compilation executes rapidly and completes with zero errors.

Limitations and Operational Precautions

When managing OS compilations in production environments:
1. Never Perform Full OS Download on Active Single Stations: Executing a complete OS compilation generates new internal tag IDs. Downloading an 'Entire OS' requires stopping WinCC Runtime, which leaves operators blind on non-redundant Single Stations. Schedule downtime or verify redundancy.
2. Redundant OS Server Download: In redundant OS pairs, download the complete project to the Standby Server first, wait for redundancy synchronization to complete, execute an operator switchover, and then download to the Partner Server.
3. Avoid Interrupted Compilations: Never terminate s7tosx.exe via Windows Task Manager during an active OS compile. Hard termination corrupts the delta tracking table and forces another full compile.

Engineer FAQ

Why did clicking 'OK' on error 1739:10 allow the compilation to continue?

Clicking 'OK' causes the compiler to bypass the corrupted delta record and fall back to scanning the remaining chart container. However, the resulting OS tag database may be incomplete, leading to unlinked tags in runtime faceplates.

Does error 1739:10 indicate an issue in the PLC controller program?

No. The error is strictly confined to the engineering station's OS compilation database on the ES PC. The PLC controller code continues running normally in the field.

What causes error 1739:10 when moving a project from SP2 to SP4?

PCS 7 Service Packs frequently update internal system function blocks and UDT definitions. If old block type handles remain cached in the delta index without a full compile, the compiler rejects them as 'invalid object types'.