Does an ES/OS Master and Standby Setup Change How PCS 7 Loads the AS?

No. The special loading considerations for an ES/OS master and OS standby apply to transferring the OS project; they do not, by themselves, change the AS program download workflow. Load CFC/SFC programs to the AS through the CFC/SFC download functions, and determine whether a change-only load is permitted from the actual program, CPU and PCS 7/CFC version. Some SFC modifications require the affected sequence to be deactivated or stopped, while other changes have different requirements.

What the ES/OS Arrangement Changes

An Engineering Station (ES), OS master and OS standby arrangement concerns how operator-station project data is assigned and transferred to the OS computers. Siemens' PCS 7 Operator Station V7.0 SP1 manual treats the destination OS and standby OS as OS-project settings: the master OS is assigned its target computer and, for a redundant server, its standby OS. These OS target/standby settings are separate from compiling and downloading CFC/SFC program data to an AS.

AS Download Uses the CFC/SFC Workflow

For an AS program created with CFC/SFC, use the supported CFC/SFC loading functions, such as PLC > Download from the CFC/SFC editor or the corresponding SIMATIC Manager compile-and-download functions documented for the installed PCS 7 release. Siemens' CFC manual states that its download function maintains consistency between engineering data and CPU data. The PCS 7 V9.1 readme also enumerates CFC/SFC download functions, but the source question does not state a version; confirm the exact commands in the installed release's documentation.

Decide Whether a Change-Only Download Is Allowed

Do not assume that every CFC change can be downloaded while the AS remains in RUN. The download dialog and compiler determine which load modes apply to the specific configuration. Siemens' CFC documentation describes an entire-program load as requiring CPU STOP and describes a change-only load as possible in RUN-P for supported changes, while warning that STOP cannot be fully excluded in all situations. More recent CFC documentation makes RUN download eligibility depend on CPU and whether the change can be loaded without a complete program download. Follow the actual compile/load result for the installed CPU and CFC version.

Treat SFC Changes According to Their Type

The original discussion mentions stopping a changed SFC as a precaution. Siemens' older PCS 7 Engineering System manual distinguishes changes: changes to SFC chart topology require the affected chart to be deactivated for a changes-only load; modifications to an SFC type interface require the SFC instances to be deactivated and execution stopped on the CPU. These examples do not establish that every edit to any SFC always requires a stop. Check the change-specific compiler/load requirements and plant operating procedure.

Procedure for an AS Program Change

Identify the affected AS, CPU and CFC/SFC charts; confirm the installed PCS 7 and CFC versions.
Compile the intended CFC/SFC scope and review the generated messages and load requirements.
Confirm that the plant is in an approved state for the indicated operation. If the tool requires STOP, chart deactivation or sequence stoppage, coordinate the process impact before proceeding.
Start the download only through the supported CFC/SFC or SIMATIC Manager loading functions for that release. Select the exact scope and mode required by the compiler and project.
Review the completed download status and any diagnostics. Return affected sequences to their approved operating state and confirm expected AS behavior using the site's commissioning or change-control checks.

Expected Results and Verification

A successful AS program download updates the targeted CPU program according to the selected scope and mode. Verify the target AS/CPU, completion messages, relevant CFC/SFC diagnostics and the process behavior of affected logic. An OS project transfer is a separate operation: successful OS loading alone does not demonstrate that an AS program change was downloaded, and an AS download does not establish that the OS project was transferred to both redundant stations.

Verification

Before loading, confirm that the target selection is the intended AS and that the CFC/SFC compile reports the expected load scope. Afterward, confirm the load result for that CPU and inspect affected logic or sequences using the site's approved verification procedure. For OS transfers, verify the destination and standby OS handling separately using the appropriate release-specific OS loading instructions.

Limitations and Operational Precautions

The ticket does not identify the PCS 7, CFC, CPU or OS versions, the specific OS loading rule being referenced, or the AS change type. The detailed load-mode examples cited here come from Siemens manuals for older PCS 7 versions, so their exact interface and applicability must be checked against the installed release. A download can affect process availability; do not infer that RUN loading is safe or available merely because the system has redundant OS servers. Take a project backup and follow site change-control, process-state and rollback requirements.

Engineer FAQ

Does an OS master/standby rule apply to the AS download? No; OS project transfer and AS program download are separate workflows.

Can I keep the AS in RUN for every CFC change? No. RUN loading depends on the CPU, change set and installed CFC/PCS 7 support; review the compile and download requirements.

Must every changed SFC be stopped? Not as a blanket rule. Some SFC topology or interface changes require deactivation or stopped execution; determine the requirement for the exact change.

Does loading the OS update the AS program? No. An OS project transfer does not replace the separate CFC/SFC-to-CPU download.

Does loading the AS transfer changes to both redundant OS stations? No. OS target and standby handling must be managed in the OS project loading workflow.

Technical References

Siemens, Process Control System PCS 7 – Operator Station, V7.0 SP1, section 5.1.6 “How to Specify the Path for Loading the Destination OS and Standby OS”: https://cache.industry.siemens.com/dl/files/758/27002758/att_53485/v1/ps7phosb_en-US.pdf
Siemens, Process Control System PCS 7 – Engineering System, section 7.11.2.11 “How to Download CFC Charts to the CPU” and section on downloading SFC charts: https://cache.industry.siemens.com/dl/files/448/15229448/att_77191/v1/PHB_PCS7_e.pdf
Siemens, CFC for SIMATIC S7 (V9.0 SP2), Function Manual, 06/2018, section 10.5 “Handling block types”: https://support.industry.siemens.com/cs/attachments/109759209/s7cfcs7b_en-US.pdf

Does an ES/OS Master and Standby Setup Change How PCS 7 Loads the AS?