Resolving WinCC 'Trends Online' Missing License Errors and Configuring Historical Archive Trends in PCS 7

In SIMATIC PCS 7 (v6.1 through v8.2), when opening the toolbar 'Trends Online' tool triggers a license missing dialog while individual faceplate trends open without error, the issue occurs because 'Trends Online' is an Advanced Process Control (APC) system option requiring a dedicated 'Advanced Process Control' license in Automation License Manager (ALM). Furthermore, when faceplate trend windows display only live real-time values starting from the moment of opening rather than past historical curves, the condition is caused by the tag's Data Source being locked to 'Online Tags'. To display historical trend curves, the analog variable must be configured with the 'S7_archive' attribute in CFC, compiled into WinCC Tag Logging, and linked as an 'Archive Tag'.

WinCC Trend Controls - Faceplate Trends vs Toolbar 'Trends Online'

In SIMATIC PCS 7 Operator Stations, trend visualization is implemented across two distinct interfaces:
1. Faceplate Trend Controls (@pg_*.pdl):
- Embedded directly within standard APL faceplates (such as MonAnL, PIDConL, or classic MeasMon).
- Utilizes standard WinCC OnlineTrendControl objects included within base WinCC Runtime licenses.
- Evaluates process trends across configurable time windows (e.g. 10 minutes, 1 hour, 8 hours).
2. Toolbar 'Trends Online' Application:
- A specialized standalone multi-tag analysis tool launched from the main WinCC runtime navigation toolbar.
- Enables operators to combine arbitrary analog process variables from different controllers onto a single synchronized multi-axis trend sheet.
- Operates as part of the Advanced Process Control (APC) suite, which requires explicit license validation in Automation License Manager upon launch.

Advanced Process Control (APC) Licensing Prerequisites

Commercial Accuracy Disclaimer: Software order numbers (MLFBs), package structures, and hardware capacity prerequisites vary across PCS 7 versions and hardware platforms. System integrators must confirm exact software entitlements and licensing requirements against the official Siemens Catalog CA 01 and obtain an authorized Siemens distributor quotation prior to purchasing.

When an operator clicks the toolbar trend icon and WinCC displays:

License missing: Advanced Process Control / Trends Online

License Requirement in ALM:
The station must possess the Advanced Process Control license key (e.g. MLFB 6ES7658-2DF08-0YB0 or release-specific equivalent) installed on the local drive.
In older PCS 7 releases (such as v6.1 or v7.0), installing a license key belonging to a newer or older major version causes ALM license mismatch errors. The license major version in ALM must align with the installed PCS 7 software release.

Configuring Historical Archiving for APL Analog Variables (S7_archive)

A frequent operational issue occurs when an operator opens a faceplate trend window and observes that historical curves prior to the current minute are completely missing:
1. The 'Online Tags' Default Mode:
- If a tag is connected to the trend control as an Online Tag, WinCC reads values directly from volatile Data Manager memory (CCDMCommand.exe).
- The trend displays values only from the exact second the faceplate was opened; closing and reopening the faceplate erases the curve.
2. Converting to 'Archive Tags' via S7_archive:
- To provide true historical continuity, the tag must be stored in the WinCC Tag Logging database.
- In the CFC chart, open the analog block (e.g. MonAnL or custom Meas_Monitor).
- Ensure the process output pin (PV_Out.Value) has system attributes:
text S7_m_c := 'true' S7_archive := 'true' (or 'shortterm')
- When Compile OS runs, the compiler automatically inserts the tag into Tag Logging > Archives, creating an internal archive tag.
- In Graphics Designer, the faceplate trend control automatically detects the archive tag, unlocks the disabled data source field, and switches from 'Online Tags' to Archive Tags, rendering full historical curves.

WinCC Trend Display Modes and Licensing Comparison Table

The following table compares trend display mechanisms in SIMATIC PCS 7:

Trend Visualization FeatureData Source UtilizedHistorical Data Available?Required Software LicenseAccess MethodFaceplate Trend (Online Mode)Online Tag (RAM Data Manager)NO (Only data since window open)Standard WinCC RTOpen block faceplate > Trend tabFaceplate Trend (Archive Mode)Archive Tag (Tag Logging SQL)YES (Days, weeks, or months)Standard WinCC RTOpen block faceplate > Trend tabToolbar 'Trends Online'Multi-Tag Archive & OnlineYES (Multi-curve comparison)Advanced Process ControlMain runtime toolbar buttonProcess Historian TrendProcess Historian SQL DatabaseYES (Multi-year enterprise data)Information Server ClientWeb browser via Information Server

Verification

To confirm that trend licenses and historical archiving are fully operational:
1. Open Automation License Manager: verify that the Advanced Process Control license is present with status Valid.
2. Click the toolbar Trends Online button in WinCC Runtime: confirm that the multi-tag trend window opens cleanly without license error popups.
3. Open an analog faceplate (e.g. TI_101):
- Confirm that the trend curve displays historical data spanning back before the window was opened.
- Check the trend legend: verify that the tag name references the Tag Logging archive path (e.g. SystemArchive\TI_101.PV_Out#Value).
4. Click the ruler icon in the trend control: verify that historical timestamps and values can be inspected interactively.

Limitations and Operational Precautions

When configuring historical trends in WinCC:
1. Archive Tag Licensing: Every analog variable marked with S7_archive consumes a WinCC Archive Tag license. Verify in ALM that your installed WinCC Archive Tag package (e.g. 512, 1500, or 5000 archive tags) covers all configured trend variables.
2. Avoid Fast Acquisition for Slow Processes: Setting temperature tags to archive at fast 100 ms intervals bloats the SQL Server database unnecessarily. Configure slow thermal tags for 10-second or 60-second cyclical logging.
3. Delta Compilation Required: Adding S7_archive to a block pin requires an OS Changes Compile and online download to OS servers before archive tags become available in runtime.

Engineer FAQ

Why is the 'Data Source' dropdown disabled in my faceplate trend window?

APL faceplates automatically set the data source. If the tag is not registered in WinCC Tag Logging, the script locks the data source to 'Online Tags'. Once the tag is archived, the script unlocks and switches to 'Archive Tags'.

Can I view historical trends if the PLC was disconnected yesterday?

WinCC can display historical data logged prior to the disconnection. However, during the outage, the trend displays a flat line or gap representing invalid data quality.

What does the Advanced Process Control package include?

APC includes advanced multi-variable predictive controllers, Smith predictors, gain scheduling blocks, and advanced diagnostic tools like 'Trends Online'.

Does changing a tag from Online to Archive require a controller CPU download?

No. Adding the S7_archive attribute modifies only the WinCC Tag Logging database. It requires an OS Changes Compile, but zero downloads to the S7 controller.