How to Check PCS 7 V9.1 OS Redundancy Before Stopping Runtime

A warning when stopping WinCC Runtime on one PCS 7 V9.1 redundant OS server means PCS 7 has detected a redundancy problem; it does not alone prove that all OS clients will become unusable. Continued operation depends on the partner server being healthy, connected to the required AS, and available to the clients. Check the client's connected-server status, the redundancy status, process-control messages, and archive synchronization before stopping either server.

What the stop-runtime warning means

PCS 7 checks for a redundancy problem when Runtime is deactivated on one of a redundant server pair. A warning therefore calls for diagnosis of the partner and system state; it is not a guarantee that the partner can take over. Siemens documents a case where the standby server has lost its AS connection: stopping the master in that state leaves the plant without operator control because the standby has not established process communication.

A client may nevertheless remain operable through the other server if that server is available and the client can use it. In the reported case, a second client remained operable after the ES/OS master Runtime was stopped. That observation applies to that installation; it does not establish that the redundancy was healthy or that another project will behave the same way.

Check which OS servers the clients can see

Before deactivating Runtime, inspect the PCS 7 area overview's connected-server status display on an OS client. Siemens describes the status indication as showing whether the monitored OS servers are in Runtime, have status “OK,” and have fault-free network connections. Open its detail window and confirm both members of the redundant pair are represented as expected.

If the normal area-overview control is missing, do not infer redundancy health from its absence. The PCS 7 V9.1 Compendium Part D documents checking the server's redundancy group/system variables while Runtime is active, including @RedundantServerState: 1 = master, 2 = standby, 3 = fault, 4 = standalone. The V9.1 manual also documents an area-overview server-status button when the OS server is configured as an operator station. Exact display availability depends on project configuration.

Verify the standby server can serve the plant

While both runtimes are active, confirm the standby server's runtime and redundancy state from the client status display and server-side redundancy diagnostics.
Inspect PCS 7 process-control messages for the server being considered for shutdown. Siemens' V9.1 manual recommends reviewing those messages before deactivating a server and resolving relevant critical messages; filter by the computer name when useful.
Confirm that the standby has established process communication to every AS it must serve. A running Runtime or “standby” label alone does not prove AS communications are healthy.
Check client preferred-server settings and confirm the clients have a usable connection to the partner. Clients switch to their partner when the preferred server fails, but this depends on the configured client-server topology.
Check that redundant archive synchronization has completed before stopping the master. Siemens warns that deactivating the master before synchronization completes can cause data loss in its described scenario.

If any of these checks fail or the warning persists without an understood cause, postpone the shutdown and resolve the redundancy issue.

Plan a controlled Runtime shutdown

For planned deactivation of a redundant pair, Siemens' PCS 7 Compendium Part D directs the operator to check plant and client configuration and verify that the partner is operating correctly. It states not to deactivate both computers of a redundant pair at the same time and to deactivate the standby server first during the described maintenance procedure. Keep the partner running and verify the plant's operation after the first server is stopped.

The forum question concerns stopping the ES/OS master to make a project backup, but it does not specify the project-archive operation or its exact prerequisites. Do not stop a master merely to “start archiving” based on this thread. Follow the applicable PCS 7 project-backup procedure separately and coordinate any OS Runtime shutdown with operations.

How to interpret @RedundantServerState

In PCS 7 V9.1, the Compendium lists @RedundantServerState values as 0 = undefined/starting, 1 = master, 2 = standby, 3 = fault, and 4 = standalone. Siemens says these server variables are checked on the OS server to determine its redundancy status. The area-overview connected-server indicator is a separate client-side check. Neither one replaces confirming AS process communication, client connectivity, or synchronization status.

Verification

Before and after the planned shutdown, verify that the remaining server is in Runtime, has a valid redundancy/operating state, communicates with its assigned AS, and is visible to the relevant OS clients. Check process-control messages and confirm archive synchronization before taking the master offline. Afterward, confirm client area availability, message handling, and the expected server status. Restore the stopped station using the release-specific procedure, then verify both servers and synchronization before considering redundancy restored.

Limitations and Operational Precautions

This procedure is scoped to PCS 7 V9.1 documentation. The source does not reproduce the exact warning text, identify which server was master at the time, or provide the topology, client package state, AS assignments, or event logs. Consequently, the warning's specific root cause cannot be identified from the discussion alone.

Do not interpret a green indicator or a client that remains operable as proof that all required AS communications, archives, or redundant functions are healthy. Stopping a server can affect areas whose standard server is unavailable; redundancy only preserves functions supported by the running partner. Never stop both members of a redundant pair together when continued operation is required, and do not dismiss a redundancy fault without diagnosing it.

Engineer FAQ

The warning indicates that the runtime-stop check found a redundancy problem; the consequence depends on the partner's actual health and client/AS connectivity. A client status display, server-side redundancy state, process-control messages, and archive-synchronization messages provide separate evidence and should be reviewed together.

Technical References

Siemens, SIMATIC PCS 7 Compendium Part D – Operation and Maintenance (V9.1), Operating Manual, 03/2022, A5E42576194-AA, §§4.2.5–4.2.9 and 4.2.11, pp. 20–31; §4.2.7 lists redundancy variables and explains the Runtime-deactivation check: https://cache.industry.siemens.com/dl/files/463/109808463/att_1099157/v1/pcs7_compendium_part_d_en-US_en-US.pdf

This V9.1 manual supports the stated status checks, shutdown cautions, and redundancy scenario. No exact warning wording was available in the source.

How to Check PCS 7 V9.1 OS Redundancy Before Stopping Runtime