Fix "No Connection to Data Server" in a Migrated PCS 7 WinCC Runtime

When WinCC Runtime reports “No connection to data server” after a PCS 7 migration, first confirm whether the runtime computer is intended to act as the local OS server or connect to a separate server. In one PCS 7 V9.0 SP3-to-V9.1 SP1 case, removing an incorrect OS path for Runtime hosted on the Engineering Station, recompiling and restarting resolved the alarm-availability issue. Apply that correction only when it matches the project's actual station role.

Establish the station role

Determine whether Runtime is intended to run as a local OS on the Engineering Station, a separate OS server or an OS client. The OS target path and server-package configuration must match that architecture. The case involved a VM running PLCSIM and WinCC Runtime after migrating PCS 7 V9.0 SP3 to V9.1 SP1.

Reported resolution for a local Runtime

The initial reply proposed deleting <osname>.dcf, recompiling with server packages, loading the OS and restarting. After the user clarified that the ES hosted the OS Runtime, the later response was to remove the configured OS path and recompile. The user confirmed that this resolved the message. The thread therefore confirms the OS-path correction for that local-host scenario; it does not establish .dcf deletion as necessary or generally safe.

Check and correct the OS target

Back up the PCS 7 project and identify the OS object, configured target computer/path and actual Runtime host.
Compare the target OS properties with the project architecture. Confirm whether the ES is intentionally the local OS server or whether a separate OS server is required.
If the ES is the intended local Runtime host and the configured path is incorrect, correct the target using the migration and OS configuration procedure for the installed PCS 7 version. Do not remove a valid remote-server target from a client/server system.
Compile the OS server and review diagnostics, including server-package configuration.
Deploy the updated OS configuration to the intended runtime station and restart Runtime during an approved maintenance window.

Do not delete configuration files generically

The .dcf deletion suggestion was made before the VM/local-server role was clarified. The confirmed result followed removal of the OS path. Retain project/configuration files unless version-specific Siemens documentation or diagnostics identify them as the cause.

Virtual-machine checks if the path correction is insufficient

Confirm the VM computer name, selected communication interfaces, OS target path, server packages and intended local/remote data-server relationship. The fact that PLCSIM and Runtime share one VM does not by itself prove PLCSIM caused the data-server message.

Verification

After deployment and restart, confirm Runtime connects to the intended data server and that alarms become available. Check WinCC/PCS 7 diagnostics and verify any client/server station points to the intended OS server. A running CCAlgRtServer.exe process alone does not prove that the project is connected correctly.

Limitations and Operational Precautions

This resolution is confirmed for one migrated PCS 7 V9.0 SP3 to V9.1 SP1 project with local Runtime on the ES. The exact OS property, topology and cause of the stale path were not documented. Recompilation, deployment and restart can affect operator stations; preserve a backup and follow site change control.

Engineer FAQ

What fixed the reported case? Removing the incorrect OS path for an ES-hosted local Runtime, then recompiling and restarting.

Should the .dcf file be deleted? Not as a generic remedy; the confirmed correction in the clarified scenario was the OS-path change.

Does this apply to remote OS servers? No. Client/server projects may need a valid remote target and server packages.

Does CCAlgRtServer.exe running prove connection? No. Verify Runtime data-server state and alarm availability.

Does sharing the VM with PLCSIM identify the cause? No. The source does not show that PLCSIM caused the message.

Technical References

Siemens, PCS 7 Engineering System V9.0 SP3 Configuration Manual, station and OS configuration context: https://support.industry.siemens.com/cs/attachments/109800501/ps7phesb.pdf
Siemens, PCS 7 Operator Station V9.1 SP1 Configuration Manual, OS station/server configuration context: https://support.industry.siemens.com/cs/attachments/109805404/ps7phosb_en-US.pdf