WinCC Flexible SQLDMO Server Class Initialization Error: Repair

WinCC Flexible SQLDMO Server Class Initialization Error: Repair Procedure

The "Cannot initialize SQLDMO server class" message is one of the most persistent startup faults encountered on engineering stations running WinCC Flexible 2005 / 2007 / 2008 on Windows XP Professional SP2 (and on early Windows 7 configurations where compatibility layers are still in use). The fault is not caused by WinCC Flexible itself in 95 % of cases; it is triggered by the embedded Microsoft SQL Server 2000 Desktop Engine (MSDE) instance that WinCC Flexible uses for project, recipe, and audit storage. When the MSDE instance is corrupt, unregistered, or its supporting COM layer (SQLDMO.dll) is missing, WinCC Flexible cannot initialize its database layer and refuses to open or create any project.

This reference documents the official Siemens three-step remediation from the WinCC Flexible Readme, the underlying architecture of the failure, the prerequisite check that prevents recurrence, and the verification commands that confirm the fix. It is intended for commissioning engineers, service technicians, and system integrators working with SIMATIC HMI configuration workstations.

1. Problem Definition

When WinCC Flexible is launched, or when a new project is being created, the following dialog appears:

Cannot initialize SQLDMO server class.
This usually indicates a corrupt Database installation.
Try to reinstall the WinCC flexible database server (see Readme)

The dialog originates from the WinCC Flexible project database access layer. It can occur in three operational states:

2. Root Cause Analysis

WinCC Flexible 2005 and 2007 do not use a full SQL Server. They bundle Microsoft SQL Server 2000 Desktop Engine (MSDE), version 8.00.760 or later, installed as a named instance with the literal identifier:

The instance stores project files, library objects, recipes, logs, and audit trails. Communication between the WinCC Flexible front-end and MSDE goes through:

• SQLDMO.dll — SQL Distributed Management Objects (COM). Provides the COM-callable surface used by the WinCC Flexible engineering front-end and by Hmies.exe (the HMI engineering service executable).
• SQLSRV32.dll — the SQL Server ODBC driver.
• SQLUNIRL.dll — the SQL Server Unicode layer.
• MSADO15.dll / msado21.tlb — ADO 2.1 dependencies referenced from the WinCC Flexible project loader.

When the COM registration of SQLDMO.dll fails (missing registry keys under HKEY_CLASSES_ROOT\SQLDMO.Application or missing file), when the MSDE named instance is not registered as a Windows service, or when the master / msdb / tempdb system databases of MSSQL$WINCCFLEXIBLE are damaged, the SQLDMO call from WinCC Flexible returns E_FAIL and the dialog is raised.

2.1 Files and Registry Keys to Verify

3. Prerequisites for Repair

Before touching the SQL layer, confirm the following. Skipping these is the single most common reason the error returns after a successful reinstall:

1. Local Administrator rights on the engineering PC. Standard users cannot register COM components or write to %programfiles%\Microsoft SQL Server.
2. Internet Explorer 6.0 or higher installed. WinCC Flexible relies on IE6+ for HTML-based help, MSI bootstrapper, and MDAC installation hooks.
3. File and Printer Sharing for Microsoft Networks enabled on the LAN adapter. MSDE uses named pipes (\\.\pipe\sql\query) but the WinCC Flexible bootstrap verifies that NetBIOS / SMB is bound before allowing install to proceed.
4. Message Queuing Services (MSMQ) installed and started. WinCC Flexible 2005 SP1+ uses MSMQ for distributed audit-log fan-out. Without it, the install routine can roll back partially and leave the SQL instance half-installed.
5. Installation order strictly enforced on green-field installs: STEP 7 → ProTool (legacy projects) → WinCC Flexible. STEP 7 V5.4 + SP1 (K5.4.1.0) and similar updates are known to disturb the SQLDMO COM registration; always reinstall WinCC Flexible after such an update.
6. All WinCC Flexible CDs available, in particular CD_2 which carries the MSDE image under WinCCflexible\setup\MSDE\disk1\Setup.exe.

4. Step-by-Step Repair Procedure

The Siemens Readme procedure is a strict three-step sequence. Steps must be executed in this order, with a reboot between each cluster where indicated. The full procedure is reproduced and annotated below.

4.1 Step 1 — Uninstall the WinCC Flexible instance of MSDE

1. Insert CD_2 of the WinCC Flexible installation set into the CD drive. Note the drive letter; the example below uses D:.
2. Open Start → Run…, type cmd, and press Enter.
3. Switch to the CD and descend into the MSDE installation folder:

   D:\> cd D:\WinCCflexible\setup\MSDE\disk1
   D:\WinCCflexible\setup\MSDE\disk1>

4. Execute the uninstall routine. The /z"UTAH_U" switch is the MSDE Setup install-time property that signals Unattended Uninstall of the named UTAH-coded (SQL Server 2000) instance:

   D:\WinCCflexible\setup\MSDE\disk1> Setup.exe /z"UTAH_U"

5. Wait for the dialog "Uninstall completed successfully" (or its unattended equivalent exit code). Do not interrupt.

4.2 Step 2 — Delete residual installation elements

The MSDE uninstall routine sometimes leaves the data, log, and registry folders behind. These leftovers will be detected by the fresh installer and block the install with a "Setup has detected a previous installation" error. Remove them as follows:

1. From the same elevated cmd window, change to the SQL Server program folder:

   C:\> cd "%programfiles%\Microsoft SQL Server"
   C:\Program Files\Microsoft SQL Server>

2. If this folder no longer exists, the uninstall completed fully. Skip to Step 4.3.
3. If the folder is present, delete the WinCC Flexible instance folder recursively and silently:

   C:\Program Files\Microsoft SQL Server> rd /s /q MSSQL$WINCCFLEXIBLE

4. Inspect the 80 subfolder. Only delete it if it contains no other entries. If 80 is shared with another SQL product (a separate WinCC instance, a third-party SQL tool, etc.) leave it alone — removing shared runtime files breaks the other instance:

   C:\Program Files\Microsoft SQL Server> dir 80

5. Optionally, remove the orphaned service registration:

   C:\> sc delete MSSQL$WINCCFLEXIBLE

   Use this only if the service still appears in services.msc after the uninstall.
6. Reboot the engineering PC to ensure the Windows Service Control Manager releases any locks on sqlservr.exe image handles.

4.3 Step 3 — Reinstall the WinCC Flexible instance of MSDE

1. Return to the MSDE setup folder on CD_2:

   C:\> D:
   D:\> cd WinCCflexible\setup\MSDE\disk1
   D:\WinCCflexible\setup\MSDE\disk1>

2. Run the setup. Per the WinCC Flexible Readme, the same UTAH_U property string is used on the install pass on certain CD revisions. Use the command that matches your Readme. The typical install command is:

   D:\WinCCflexible\setup\MSDE\disk1> Setup.exe /z"UTAH_U"

3. The setup copies the MSDE binaries, creates the MSSQL$WINCCFLEXIBLE instance, attaches master, model, msdb, tempdb, and registers SQLDMO.dll.
4. If the install fails partway, the setup log is written to %windir%\sqlstp.log and %windir%\setupapi.log. Both should be reviewed before re-running.
5. Reboot when prompted.

5. Verification Procedure

After the reboot, validate the fix from the Windows command line before launching WinCC Flexible:

1. Service is registered and started:

   C:\> sc query MSSQL$WINCCFLEXIBLE
   SERVICE_NAME: MSSQL$WINCCFLEXIBLE
           TYPE               : 10  WIN32_OWN_PROCESS
           STATE              : 4  RUNNING

2. SQLDMO.dll is registered as a COM server:

   C:\> regsvr32 "%programfiles%\Microsoft SQL Server\80\Tools\Binn\SQLDMO.dll"
   DllRegisterServer in SQLDMO.dll succeeded.

   If the registration reports a missing dependency (typically sqlunirl.dll or msvcrt.dll), copy the dependency from the CD WinCCflexible\setup\MSDE\disk1 path into %programfiles%\Microsoft SQL Server\80\Tools\Binn and re-register.

3. ODBC connectivity to the named instance works:

   C:\> osql -S .\WINCCFLEXIBLE -E
   1> SELECT @@VERSION
   2> go

   Expected output: Microsoft SQL Server 2000 - 8.00.XXXX (Desktop Engine) followed by the build date. The -E flag uses Windows authentication; osql.exe is shipped in the MSDE Binn folder.

4. WinCC Flexible launches without the dialog: start the WinCC Flexible ES, choose File → New, and create a temporary project. If the project wizard reaches the device-selection screen without re-raising the SQLDMO dialog, the fix is complete.

6. Alternative Repair Methods

If the three-step Siemens procedure does not resolve the fault, the following supplementary actions are typically deployed by service technicians in the order listed.

6.1 Re-register SQLDMO and dependent COM libraries

regsvr32 /u "%programfiles%\Microsoft SQL Server\80\Tools\Binn\SQLDMO.dll"
regsvr32 "%programfiles%\Microsoft SQL Server\80\Tools\Binn\SQLDMO.dll"
regsvr32 "%programfiles%\Microsoft SQL Server\80\Tools\Binn\SQLUNIRL.dll"
regsvr32 "%programfiles%\Common Files\System\Ole DB\oledb32.dll"

6.2 Repair the MDAC (Microsoft Data Access Components) stack

WinCC Flexible 2005 depends on MDAC 2.8 SP1. A damaged MDAC stack can be repaired without uninstalling SQL Server by downloading and re-running the MDAC Component Checker from Microsoft, which detects and re-registers missing MDAC DLLs. After the repair, re-run the SQLDMO registration step above.

6.3 Clean the residual user database files

If the previous MSDE instance left orphaned .mdf / .ldf files under %programfiles%\Microsoft SQL Server\MSSQL$WINCCFLEXIBLE\Data, the new installer may attach them and fail on a version mismatch. Move the entire Data folder aside before reinstall:

move "%programfiles%\Microsoft SQL Server\MSSQL$WINCCFLEXIBLE\Data" "%programfiles%\Microsoft SQL Server\MSSQL$WINCCFLEXIBLE\Data.bak"

6.4 Escalation path

If the procedure still does not resolve the fault, escalate to the Siemens Industrial Online Support portal with:

• The full %windir%\sqlstp.log from both the failed and successful install attempts.
• The services.msc screenshot of the MSSQL$WINCCFLEXIBLE service entry.
• The output of osql -S .\WINCCFLEXIBLE -E -Q "SELECT @@VERSION".
• The Windows event log (Application channel, filter by source MSSQL$WINCCFLEXIBLE).

The SIMATIC hotline can provide a manual Microsoft SQL Server installation recipe (separate from the MSDE bundle) tailored to WinCC Flexible; this is referenced in the original Siemens support correspondence and is the recommended escalation route for repeated failures.

7. Troubleshooting Matrix

8. Prevention and Long-Term Hygiene

• Document the install media revision of every WinCC Flexible CD in the engineering-station handover pack; mismatched CDs are a recurring fault source.
• Avoid installing other Microsoft SQL Server versions on the same engineering PC. MSDE 2000 and SQL Server 2005/2008 Express can coexist in principle, but the SQLDMO COM class from MSDE 2000 is the one WinCC Flexible loads, and a newer install can shadow the COM registration.
• After any Windows servicing update that lists SQLDMO.dll, sqlsrv32.dll, sqlunirl.dll, or msado15.dll in its manifest, re-run the SQLDMO re-registration (section 6.1).
• Take a disk-image snapshot of the engineering PC immediately after a clean, fully-working WinCC Flexible install; rollback from such an image is faster than re-running the SQLDMO procedure.
• For audit-bound applications, enable MSMQ before the first WinCC Flexible project is created. Adding it later requires project-side re-configuration.

9. Cross-Reference: Related WinCC Flexible Database Errors

The following SQLDMO-adjacent error strings can be resolved with the same three-step procedure, but each has a distinct nuance:

10. Summary Checklist

• [ ] Confirm administrator rights, IE6+, File & Print Sharing, MSMQ
• [ ] Insert WinCC Flexible CD_2
• [ ] Step 1 — uninstall: Setup.exe /z"UTAH_U" from WinCCflexible\setup\MSDE\disk1
• [ ] Step 2 — delete MSSQL$WINCCFLEXIBLE instance folder, conditionally delete 80
• [ ] Reboot
• [ ] Step 3 — reinstall: Setup.exe from the same path
• [ ] Reboot
• [ ] Verify: sc query, regsvr32, osql -E, WinCC Flex project creation

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