How to Update Block Tag Names and Icons Without Losing OS Delta Download Capability in PCS 7

In SIMATIC PCS 7, renaming technological blocks in CFC does not mandate a full OS compilation that invalidates online delta download capability. By selecting 'Compile OS -> Changes only' and ensuring that the 'Tags and messages' scope option is selected in the wizard, the compiler successfully updates the modified tag names in WinCC Tag Management while preserving delta download capability. Furthermore, in PCS 7 V8.1 and higher, block icons and screen tag prefixes can be updated directly from the Plant Hierarchy using the 'Create/Update Block Icons' function without performing an OS compilation or causing server downtime.

Plant Hierarchy Tag Name Generation and Delta Download Rules

In SIMATIC PCS 7, process variable names in WinCC are derived hierarchically from the Plant View (Technological Hierarchy):
Tag Name = [Plant Area]/[Unit]/[Function]/[CFC Chart Name]/[Block Instance Name]

When an engineer renames a technological block or chart (e.g., correcting a typographical error from Pmp_01 to Pump_101), the new tag name must propagate to WinCC Tag Management, Alarm Logging, and graphic block icons.

Engineers frequently encounter a critical dilemma:
* After renaming the block, an OS compile is required.
* If the engineer executes Compile OS -> Entire OS, SIMATIC Manager issues a stern warning:
'Compiling entire OS will lead to the loss of the online download capability of the OS.'
* In an active production plant, losing delta download capability forces a complete project reload requiring runtime deactivation, which risks production interruptions.

The Risk of 'Compile Entire OS' in Running Plants

Why does compiling the entire OS destroy online download capability?
1. Delta Tracking Journal Invalidation: WinCC maintains transaction logs tracking incremental differences between the engineering database (CS) and the runtime database (RT).
2. Resetting Compile Timestamps: Executing an 'Entire OS' compile resets the internal database generation timestamp. The target OS Server will reject any subsequent delta download because its runtime timestamp no longer matches the offline project history.
3. Mandatory Full Download: Once an Entire OS compile is performed, the next download must be an Entire OS download, requiring the target WinCC runtime to be deactivated.

Procedure to Update Tag Names While Preserving Delta Downloads

To update tag names and block icons on the OS without sacrificing delta download capability, use this workflow:

Step 1: Update Block Icons via Plant Hierarchy

In PCS 7 V8.1 and higher, block icons on process screens can be refreshed without compiling the OS:
1. In SIMATIC Manager, switch to Plant View.
2. Right-click the Plant Hierarchy folder (or the OS assignment folder) and select Plant Hierarchy -> Create/Update Block Icons....
3. In the dialog, verify the target OS and screen generation settings.
4. Click OK.
5. SIMATIC Manager scans the process pictures, updates the block icon structures, and re-links dynamic tag prefixes to the new block names.

Step 2: Compile OS with 'Changes Only' and 'Tags and Messages'

Right-click the OS Server project in SIMATIC Manager and select Compile.
In the OS Compilation Wizard:
* Select the target S7 programs.
* Under Compilation Scope, select Changes only (do NOT select 'Entire OS').
* Verify that the checkbox Tags and messages is explicitly checked.
* Verify that SFC Visualization and Picture Tree are checked if applicable.
Click Compile.
The compiler identifies the renamed blocks, updates WinCC Tag Management and Alarm Logging tables, and logs the modifications in the delta journal.

Step 3: Execute Online OS Delta Download

In SIMATIC Manager, select the OS Server object.
Select Target system -> Download to target system -> Changes only.
The delta transfer transfers modified tags, alarms, and updated picture files across the Terminal Bus.
WinCC Runtime reloads the dynamic objects in memory with zero interruption to running visualization or process control.

OS Compilation Scope and Download Impact Matrix

The following table outlines the consequences of different compilation choices when renaming technological objects:

Compilation Mode Selected'Tags and messages' Checked?Delta Download Capability Maintained?Server Downtime Required?Recommended For Live Plants?Compile OS: Changes OnlyYesYes (100% Preserved)Zero (Online Delta)Yes (Standard Practice)Compile OS: Changes OnlyNoYesZeroNo (Tags won't update)Compile OS: Entire OSYesNo (Permanently Lost)Yes (Runtime Deactivation)Prohibited during productionCompile OS: Entire (Memory Reset)YesNo (Permanently Lost)Yes (Full Sequential Reload)Maintenance windows only

Selecting 'Changes only' with 'Tags and messages' enabled guarantees continuous online update capability.

Verification

To verify that tag names have been updated successfully online:
1. Complete the 'Changes only' OS compilation and verify zero errors in the compile log.
2. Complete the 'Changes only' download to the running OS Server.
3. On an active OS Client station, navigate to the process picture containing the renamed block.
4. Confirm that the block icon displays the corrected tag name in its banner.
5. Click the block icon: verify that the technological faceplate opens smoothly and displays live process values.
6. Trigger an alarm on the block: confirm that the alarm entry in the AlarmList displays the new tag name and plant area.
7. Verify that SIMATIC Manager continues to show 'Download Changes' as an active, enabled menu option.

Limitations and Operational Precautions

If an Entire OS compile was accidentally executed, delta download is lost; in redundant systems, perform a sequential Entire OS download (Standby server first, then Master) to avoid downtime.
Renaming the top-level Plant Hierarchy folder alters the root path for hundreds of tags simultaneously, which may exceed delta quantity limits and trigger a mandatory full download.
When renaming blocks, ensure that inter-chart connections (CFC chart-to-chart connections) are compiled in the AS before compiling the OS.
Historical archive data collected under the old tag name in Tag Logging will remain under the old tag name; historical trend queries spanning the rename date may require viewing both tag identifiers.

Engineer FAQ

Why does SIMATIC Manager give a warning when selecting 'Entire OS'?

The warning alerts the engineer that compiling the entire OS destroys the internal delta change tracking history, forcing the next OS download to be a complete reload requiring runtime deactivation.

Can I rename a block in CFC and download changes to the AS without stopping the CPU?

Yes, in S7-400 and CPU 410-5H controllers, renaming an existing block instance without altering its type interface can be downloaded changes-only in RUN mode.

How do I update block icons on process pictures without running an OS compile?

Right-click the plant hierarchy folder in Plant View and select 'Plant Hierarchy -> Create/Update Block Icons'. This updates picture icons and tag links directly.