Troubleshooting Object Display Failures in SIMATIC PCS 7 CEMAT C_GROUP Faceplates on Redundant Standby OS Servers

In SIMATIC PCS 7 systems utilizing the CEMAT minerals and cement industry library, when an operator faceplate for a group control block (C_GROUP) fails to display child equipment objects (drives, dampers, and signals) on a redundant Standby OS Server restored from a disk image, the root cause is unregistered CEMAT ActiveX/OCX components (such as CematTree.ocx and CematGrp.ocx) or a mismatched WinCC Computer Name in the restored project database. Resolving this issue requires re-registering the CEMAT OCX files using Windows regsvr32, updating the local computer name in WinCC Explorer, and running the CEMAT Update Wizard to regenerate the group object tree bindings.

CEMAT C_GROUP Faceplate Architecture and OCX Dependencies

The Siemens CEMAT library (Minerals, Cement, Mining, and Glass automation) provides high-level group control function blocks, primarily C_GROUP (FB 1010). In plant operations, a single C_GROUP orchestrates starting sequences, stopping interlocks, and operational modes across dozens of connected child drives (C_DRV_1D, C_DRV_2D), dampers (C_DAMPER), and analog values (C_MEASUR):
- Dynamic Group Tree Enumeration:
* Unlike standard PCS 7 APL faceplates that display a fixed set of static variables, the C_GROUP faceplate (@PG_C_GROUP.pdl) incorporates a dynamic tree control ActiveX/OCX object (CematTree.ocx or C_TreeControl.ocx).
* When an operator opens the faceplate, the OCX queries the WinCC runtime database and local project memory to construct a hierarchical tree listing every sub-device associated with that group.
- Client-Server Data Resolution:
* The object tree queries the active WinCC Server package.
* If the underlying OCX control is missing from the Windows Registry or lacks permissions to query the local project path, the faceplate opens with empty frames, missing tree branches, or displays generic OLE container errors.

Why Disk Image Clones Cause Standby Server Display Failures

Deploying or recovering redundant WinCC OS Servers using disk imaging tools (such as Acronis True Image, Symantec Ghost, or VMware VM cloning) introduces specific configuration defects:
1. Unregistered COM/ActiveX Components:
- The master image may have been captured before CEMAT server components were fully registered, or the Windows security identifiers (SIDs) changed during sysprep, invalidating existing COM registrations for CematTree.ocx.
2. WinCC Project Computer Name Mismatch:
- The restored disk image retains the Windows Computer Name of the original Master Server (e.g. OS_SRV1).
- If the Standby PC's Windows hostname is OS_SRV2, but WinCC Explorer still references OS_SRV1 in its project properties, WinCC cannot bind local runtime channels, and CEMAT C-scripts fail when resolving local server prefixes.
3. Missing CEMAT Directory Paths:
- CEMAT requires dedicated environment variables and runtime folders (e.g. C:\CEMAT_CS\BIN and project directory GraCS\CEMAT). Cloned images often lack proper NTFS access rights on these directories.

Step-by-Step Recovery and OCX Registration Workflow

To restore proper object rendering in the C_GROUP faceplate on the Standby Server:

Update Computer Name in WinCC Explorer:
- Close WinCC Runtime.
- Open WinCC Explorer on the Standby Server.
- Right-click the Computer icon in the tree and select Properties.
- Select the listed computer name, click Properties, and click Use Local Computer Name.
- Close WinCC Explorer and reboot the computer to apply the database name binding.
Re-register CEMAT ActiveX/OCX Controls:
- Open Command Prompt as Administrator.
- Navigate to the CEMAT installation binaries directory:
cmd cd "C:\CEMAT_CS\BIN"
(or <Project_Dir>\wincproj\<OS_Name>\GraCS depending on installed CEMAT version).
- Execute registration commands for all core CEMAT OCX files:
cmd regsvr32.exe CematTree.ocx regsvr32.exe CematGrp.ocx regsvr32.exe CematDiagnosis.ocx
- Verify that Windows displays: DllRegisterServer in CematTree.ocx succeeded.
Run the CEMAT Update / Language Tool:
- In WinCC Explorer, locate the CEMAT menu add-in or run Cemat_Update.exe.
- Select Update Picture Tree and Faceplates.
- This script synchronizes internal text libraries, cross-references group block IDs, and compiles the local GraCS templates.
Synchronize Redundancy and Restart Runtime:
- Launch WinCC Runtime on the Standby Server.
- Allow WinCC Redundancy (CCRedSync.exe) to synchronize with the Master Server.
- Open the process graphic and click the C_GROUP block icon.

CEMAT Component Registration and Configuration Diagnostics Table

The following table details diagnostic checks for CEMAT group faceplates:

Component / SettingTarget LocationNormal Configured StateObserved Failure Symptom If InvalidCematTree.ocxC:\CEMAT_CS\BINRegistered via regsvr32Empty tree view in C_GROUP faceplateWinCC Computer NameWinCC Explorer > ComputerMatches Windows HostnameScripts abort; server prefix unresolvable@PG_C_GROUP.pdlProject GraCS folderValid template pictureFaceplate fails to open; 'Picture not found'CEMAT System ParameterInternal Tag @C_SYSTEMInitialized by CEMAT engineGroup start/stop buttons disabledRedundancy StateWinCC Redundancy EditorSynchronized (CCRedSync)Out-of-date child device status on Standby

Verification

To confirm that the C_GROUP faceplate has recovered full functionality on the Standby Server:
1. Open WinCC Runtime on the Standby Server and navigate to an area overview picture containing cement process lines (e.g. Raw Mill or Kiln Feed).
2. Click the block icon for a major group (e.g. RawMill_Grp).
3. Verify that @PG_C_GROUP.pdl opens instantly without OLE errors.
4. Confirm that the child equipment tree control expands cleanly:
- All associated feeder motors, lubrication pumps, and diverter dampers are listed in their configured sequence order.
- Dynamic status colors (Green for Running, Gray for Stopped, Yellow for Interlocked, Red for Fault) reflect live field status accurately.
5. Click a sub-equipment entry within the tree and verify that its specific child faceplate (@PG_C_DRV_1D.pdl) opens directly.

Limitations and Operational Precautions

When managing CEMAT installations:
1. Never Clone Servers While WinCC Runtime Is Active: Always shut down WinCC Runtime and deactivate the SQL Server instance before capturing disk images. Capturing an image while databases are mounted creates corrupt SQL transaction logs and broken COM handles.
2. CEMAT Version Alignment: Ensure that the exact CEMAT hotfix level (e.g. CEMAT V7.1 SP1 Upd 2 or CEMAT V8.2) installed on the Standby Server matches the Master Server bit-for-bit. Version mismatches cause OCX interface rejection.
3. Simatic Shell Settings: Verify that the Terminal Bus network adapter is selected in Simatic Shell on both servers to allow inter-server redundancy synchronization.

Engineer FAQ

Why did the master server display C_GROUP objects fine while the standby server failed?

Because the master server underwent the original software installation where all Windows COM/OCX components were registered, whereas the standby server was restored from an image where registry keys or local computer names were desynchronized.

Can I re-register CEMAT OCX files while WinCC Runtime is active?

No. WinCC Graphics Runtime locks OCX files in memory. Always exit WinCC Runtime before running regsvr32.

What does the 'CematTree.ocx' control do inside C_GROUP?

It dynamically parses the group's child structure tags in WinCC, enumerating all associated drive and damper instances linked to that group in the CFC charts.