Resolving WinCC RC PO Error Caused by Archive Variable License Exceeded

When a Siemens PCS 7 OS station starts WinCC Runtime, the Data Manager loading phase can abort with a WinCC RC PO Error stating the system detected more tags than the licensed Power Tag count allows. A common misdiagnosis is to assume the Power Tag license is short. In many field cases, the real constraint is the separate archive variable license dimension, which is licensed and counted independently from Power Tags. This article explains the error, the licensing architecture behind it, and the two resolution paths supported by Siemens licensing rules.

1. Problem Description

Environment: PCS 7 V7.0 SP1 with one Engineering Station / OS (ES+OS) and a redundant OS server pair. After adding new I/O, editing CFC charts, and re-compiling the OS project, WinCC Runtime fails to start. The Data Manager reports:

WinCC RC PO Error
Detected tags: 412
Licensed limit: 2000

The operator cannot acknowledge the message, and the message reappears on every Runtime start. The system appears unaffected on the configuration side because the project compiles cleanly. The OS server runs for a few seconds, then the WinCC Explorer closes the Runtime.

1.1 Symptoms Checklist

• Data Manager stalls during initial load and reports a tag-count mismatch.
• WinCC Runtime is interrupted within seconds of activation.
• The error persists after a full OS recompile and download.
• Recompiling the S7 program has no effect on the Runtime error.
• Message counter increases at each restart attempt.

2. WinCC Licensing Architecture

WinCC Runtime licensing is split across multiple independent counters. PCS 7 V7.0 SP1 enforces each counter separately at startup. Understanding the split is essential to reading the error correctly.

A project can have 412 Power Tags (well within a 2000-tag RC PO license) and still fail with an RC PO error if the number of archive variables exceeds the limit allowed by the archive counter.

2.1 How Archive Variables Are Counted

An archive variable is created when a tag is referenced in the WinCC Tag Logging editor. Each Tag Logging archive tag occupies one license slot, regardless of whether it is part of a process value archive, a compressed archive, or an alarm archive. The counter is incremented at project compilation and verified at Runtime startup.

3. Root Cause Analysis

The reported error text does not identify the counter that has been exceeded. Siemens stores the actual license diagnostics in Licens_Info.log under the WinCC Diagnose folder.

3.1 Reading the Licens_Info.log

1. Open C:\Program Files\SIEMENS\WINCC\Diagnose on the OS server.
2. Locate Licens_Info.log.
3. Search for the strings PowerTag and Archive:

Number of PowerTags (incl. archive): 412 / licensed: 2000      -> OK
Number of archive variables:        521 / licensed:   512      -> FAIL

If the archive variable line reports a value greater than 512, the Data Manager will refuse to load Runtime and emits the RC PO error. The 412 figure visible in the popup is the total PowerTag count used to compute screen / script visibility; the archive counter is what is failing.

3.2 Why the Error Appears After a Compile

Adding I/O, adding CFCs, or editing existing CFCs forces Tag Logging to recompute the archive membership. When a new tag is added under an existing archive, the archive counter grows by one. Compiling a chart that references a previously unarchived variable can also promote it to an archive tag. Therefore, a clean compile that grows the project by a small number of tags is sufficient to cross the 512 limit.

4. Diagnostic Procedure

1. Stop WinCC Runtime on the affected OS server.
2. Open the Windows Event Viewer (eventvwr.msc) and inspect WinCC entries. Look for events with source CCDataMgr and description containing the string PO Error.
3. Open C:\Program Files\SIEMENS\WINCC\Diagnose\Licens_Info.log in a text editor and confirm the archive variable count.
4. Open C:\Program Files\SIEMENS\WINCC\Diagnose\WinCC_SysLog.log and search for entries with severity ERROR around the Runtime start time.
5. Open the WinCC Configuration Studio and navigate to Tag Logging. Expand Archives and note the count of variables per archive. The sum across all archives is the licensing-relevant value.
6. Compare the count from step 5 with the value reported in Licens_Info.log to confirm there is no stale count in the project database.

5. Resolution Path A: Reduce Archive Variables to 512 or Fewer

If the project does not require a purchased archive license, the supported approach is to bring the archive variable count down to 512 or less. The following steps are performed in the WinCC Configuration Studio of the affected OS server.

5.1 Identify Unused or Redundant Archive Tags

1. Open Tag Logging in the WinCC Configuration Studio of the OS server.
2. Sort the tag list by Last Used (right-click column header → Sort).
3. Tags that have not been archived in the last 30 days are candidates for removal.
4. For each candidate, open the trend view in Runtime (or in the WinCC online trend control) to verify the tag carries process value information of operational interest.

5.2 Remove Tags From Archives

1. Right-click the tag in Tag Logging and choose Remove from archive.
2. Confirm the dialog. The tag remains in the project as a power tag (so pictures, scripts, and alarm routing still work) but is no longer counted as an archive variable.
3. Repeat for all candidates until the total count of archive variables is ≤ 512.

5.3 Re-Compile the OS

1. Open WinCC Explorer on the ES.
2. Right-click the OS server and select Compile OS → Complete compilation.
3. Download the project to the OS server.
4. Restart WinCC Runtime and confirm the RC PO error is gone.

6. Resolution Path B: Purchase an Archive Variable License

If the operational requirement needs more than 512 archive variables, purchase a WinCC archive license and install it on every Runtime machine (per Siemens license terms).

6.1 License Bundles (PCS 7 V7.0 SP1 Era)

Each Runtime machine requires its own license. In a redundant OS server pair, two licenses are required. Floating license servers (centralized license service) are supported and recommended for multi-station plants.

6.2 Installing the License

1. Copy the license file (*.zip or *.LIC) to a USB or network share accessible by the OS server.
2. Run the Automation License Manager on the OS server (Start → Siemens Automation → Automation License Manager).
3. If the license is a dongle license, install the dongle before launching the Automation License Manager.
4. Click Edit → Connect Target System, select the local OS server, and confirm the connection.
5. Drag the new license file onto the target system in the License Manager, or use License → Install to import the file.
6. Verify the archive variable count row in the Used / Licensed panel shows the new capacity.

6.3 Restart and Verify

1. Close WinCC Runtime completely on the OS server.
2. Re-start WinCC Runtime. The Data Manager should now load the full archive set without an RC PO error.
3. Confirm with Licens_Info.log that the archive counter is satisfied (the log entry will read OK).

7. Verification

8. Preventive Measures

• Use a project-wide Tag Logging review at every major CFC release. The WinCC Configuration Studio provides an Archive Statistics report that lists tag counts per archive.
• Maintain a delta log when adding I/O. Each new S7 tag added to a CFC chart may add a Tag Logging entry automatically if the chart uses standard PCS 7 archive blocks.
• Apply archive tag housekeeping before reaching the 80% threshold of the current license (for example, stop at ~400 tags on a 512 free counter).
• Use the Automation License Manager centrally and document the licensed limits in the project quality plan.
• Consider splitting long-term process values into a separate process historian (for example, PCS 7 Information Server) so the WinCC OS station archive remains within license limits.

9. Edge Cases and Related Errors

The reference link to Reaction to system errors (RT Professional) documents the WinCC client behavior when the server is unreachable. While the link targets WinCC RT Professional in TIA Portal V20, the underlying system-error handling and reconnection model apply analogously to PCS 7 V7 WinCC Runtime.

10. Field Notes for PCS 7 V7.0 SP1

• PCS 7 V7.0 SP1 is part of the legacy SIMATIC PCS 7 line. The licensing model is shared with the WinCC V7.x family, so the 512-archive default and 1500-archive smallest bundle apply.
• Migration to PCS 7 V8.x or V9.x preserves the existing archive variable count and license files. Customers adding a large I/O scope often use the migration window to consolidate or split archive sets.
• Customer-specific archive tags (created with User Archive tables or CSV export scripts) do not count toward the 512-archive variable limit. They count toward the User Archive table license, which is a separate counter.
• APL block self-archiving: starting with PCS 7 V8, several APL block types can be configured to disable automatic archive generation, which is the recommended pattern for keeping archive count down.

11. FAQ