Resolving CPU 410-5H AS RT PO Activation and Download Error (1739:60458): Parameter and Block Change (PBC) Resources

In SIMATIC PCS 7, encountering error '(1739:60458)' during CPU 410-5H AS Runtime Process Object (PO) activation or Delta Download occurs when the configured Parameter and Block Change (PBC) resources in the CPU hardware configuration are exhausted. During online PO expansion or large CFC delta downloads in RUN mode, the controller buffers block alterations in its internal PBC area. To resolve this, open the CPU 410-5H Object Properties in HW Config, navigate to the 'Cycle/Clock Memory' tab, increase the PBC resources allocation, save, and compile. If accompanied by DLL errors (s7otbxdx.dll / s7jcomfa.dll), re-register the Siemens engineering DLLs or install the latest CFC update.

CPU 410-5H Online Process Object Architecture and Activation

The SIMATIC PCS 7 CPU 410-5H Process Automation controller utilizes a flexible licensing model governed by the System Expansion Card (SEC). Rather than purchasing fixed hardware sizes, engineers scale AS Runtime Process Object (PO) capacity online in 100 PO increments using the SIMATIC Management Console (SMC) or license activation codes without shutting down the running plant.

When entering activation codes or performing subsequent delta downloads to activate new process objects in RUN, the Engineering Station can encounter the generic system error: System Error (1739:60458) with DLL s7jcomfa.dll / s7otbxdx.dll.

Understanding Parameter and Block Change (PBC) Resource Buffers

When downloading changes to an S7-400 or CPU 410 in RUN mode, the operating system must ensure bumpless transition without interrupting active control tasks. The CPU achieves this by allocating a specialized memory buffer termed PBC (Parameter and Block Change).

During a delta download, the newly compiled blocks, updated instance DB structures, and altered pointer tables are loaded into the PBC memory area. The operating system verifies structural integrity, switches execution pointers during an OB cycle boundary, and then frees the PBC memory. If the volume of blocks and parameters in the download exceeds the configured PBC buffer size, the AS abruptly rejects the download with error 1739:60458.

Root Causes: PBC Saturation vs Engineering DLL Corruption

Field analysis identifies two distinct underlying mechanisms for error 1739:60458 during PO expansion:

PBC Resource Exhaustion in CPU: The default PBC buffer allocation in HW Config is sized for small delta edits. When activating large PO blocks (e.g., adding 500 POs containing thousands of DB parameters), the delta block stream exceeds the PBC buffer limit.
Corrupted STEP 7 Communication DLLs: In certain engineering station installations, Windows update rollups or antivirus scans damage core Siemens communications binaries in %SystemRoot%\System32\ (specifically s7otbxdx.dll, s7otbxsx.dll, or s7jcomfa.dll). When the download engine attempts to serialize the block package, the DLL throws an access violation.

Step-by-Step Resolution: Reallocating PBC and Registering DLLs

To resolve error 1739:60458 and complete the PO activation:

Increase PBC Resources in HW Config:
- In SIMATIC Manager, open HW Config for the CPU 410-5H station.
- Double-click the CPU 410-5H to open Object Properties.
- Switch to the Cycle/Clock Memory (or Memory Configuration) tab.
- Locate the parameter PBC resources (Parameter and Block Change). Increase the value (e.g., doubling the current allocation or selecting the maximum allowable tier).
- Click Save and Compile.
Repair Engineering DLLs if Referenced in Log:
- If the error specifically references s7otbxdx.dll, open an elevated Command Prompt.
- Navigate to C:\Program Files (x86)\Common Files\Siemens\Bin\ (or C:\Windows\System32).
- If s7otbxdx.dll is missing or 0 bytes, restore it from the Siemens installation media or re-run the SIMATIC PCS 7 Setup in 'Repair' mode.
Apply Online PO Expansion: Open SIMATIC Management Console (SMC) or Automation License Manager. Re-apply the PO activation sequence. The AS accepts the expansion smoothly.

PBC Resource Allocation and Diagnostic Matrix

The following table compares PBC resource settings and their operational impact on Delta Downloads:

PBC Resource SettingTypical AllocationMax Delta Download ScopeImpact on Work MemoryRecommended ApplicationMinimal / Default~500 - 1,000 PBC unitsSmall logic edits (1-5 charts)Lowest AS memory overheadSmall package units / tight RAMStandard Medium~2,000 - 4,000 PBC unitsMedium modifications (10-30 charts)Negligible memory differenceStandard operational plant ASMaximum Expanded~8,000+ PBC unitsLarge commissioning batch & PO expansionMinor increase in reserved RAMMajor plant expansions / PO upgradesPBC ExhaustedSaturatedAS rejects download (Error 1739:60458)CPU remains in RUN; download failsImmediate HW Config buffer expansion

Verification

Verify successful PO expansion and download capability through the following steps:

Open SIMATIC Manager and connect online to the CPU 410-5H. Open Module Information > Performance / Memory.
Confirm that the total licensed Process Objects (PO) matches the newly expanded SEC tier (e.g., increased from 500 to 1,000 PO).
Execute a CFC Delta Compile (Changes only).
Execute PLC > Download > Changes only. Confirm that the delta download proceeds to 100% and completes without error 1739:60458.
Verify in WinCC Alarm Logging that the controller records no PBC buffer overflow alarms.

Limitations and Operational Precautions

Consider these operational rules when expanding CPU capacity:

Never Power Down During SEC Activation: Do not interrupt power or disconnect communication while the activation code is being written to the System Expansion Card, as this can corrupt the hardware license container.
Redundant H-System Alignment: In redundant CPU 410-5H configurations, ensure the System Expansion Cards on both sub-racks possess identical PO capacities; mismatched SEC capacities prevent redundant coupling.
Commercial Disclaimer: Commercial Accuracy Disclaimer: Software order numbers (MLFBs), package structures, and hardware capacity prerequisites vary across PCS 7 versions and hardware platforms. System integrators must confirm exact software entitlements and licensing requirements against the official Siemens Catalog CA 01 and obtain an authorized Siemens distributor quotation prior to purchasing.

Engineer FAQ

Where is the PBC resource parameter located in HW Config?

Open CPU Object Properties, navigate to the Cycle/Clock Memory tab, and locate the 'PBC resources' setting.

What should I do if error 1739:60458 references s7otbxdx.dll?

This indicates a corrupted Siemens engineering communication DLL. Run the SIMATIC PCS 7 Setup in 'Repair' mode or restore the DLL from the original installation media.