Troubleshooting Process Historian Historical Trend and Alarm Display on WinCC Clients

In SIMATIC PCS 7 with Process Historian (PH), OS Clients failing to display trend or alarm data older than 2 days—despite healthy PH server connections—are typically experiencing standard circular archive boundary restrictions or unconfigured historical time range selections. The local OS Server only retains 2 days of short-term data before offloading to PH. To view long-term historical data on OS Clients, set the TrendControl or AlarmControl time axis start point to a historical date greater than 2 days, and verify that the PH Server Data package is assigned to the client.

Architecture of WinCC Short-Term Circular Buffers vs. Process Historian

In SIMATIC PCS 7 high-capacity plant architectures, process archiving is divided into two distinct storage tiers:
1. Local OS Server Circular Archive (Short-Term): Managed by Microsoft SQL Server running locally on each OS Server pair. To prevent disk exhaustion and maintain fast runtime performance, local Tag Logging and Alarm Logging archives are configured as small circular segments (typically retaining 1 to 2 days of high-frequency process data).
2. Process Historian (Long-Term Enterprise Archive): Runs on a dedicated server hardware platform. It continuously receives archived process tags and alarm events from all OS Servers in real time, storing decades of plant operational data across partitioned enterprise databases.

When an operator on an OS Client opens standard WinCC TrendControl or AlarmControl and observes that trends flatline or alarms truncate exactly at the 2-day mark, the system is operating normally within its local buffer, but the client controls are not actively querying the long-term archive.

By default, WinCC controls operate in Online / Short-Term Mode, displaying only the local circular cache. To access data residing on Process Historian, the client control must be commanded to initiate an archive query spanning beyond the local circular threshold.

Archiving Architecture and Client Query Path Matrix

Understand how data requests route between OS Clients, OS Servers, and Process Historian:

Data Age RangeStorage LocationQuery Routing MechanismControl Configuration RequirementRecent 0 to 2 DaysLocal OS Server SQL DatabaseLocal WinCC Tag Logging / Alarm Logging CacheDefault rolling timeline (e.g., past 2 hours, 24 hours)Older than 2 DaysCentral Process Historian ServerRouted via OS Server or direct PH OLE DB ProviderTime axis start point configured prior to local cache cutoffSwapped / Backup SegmentsDetached PH Disk VolumesProcess Historian Database ManagerMust be attached via PH Management ConsoleAlarm Chronological ListPH Message DatabaseWinCC AlarmControl Historical Selection DialogFilter configured with explicit past Start/End Date

Enterprise licensing notice: Process Historian deployment requires dedicated Process Historian and Information Server licenses.

Configuring WinCC TrendControl and AlarmControl Historical Queries

To retrieve and display historical data from Process Historian on the OS Client:

Configure WinCC TrendControl for Historical Retrieval:
* Open the process screen containing the TrendControl in Graphics Designer (or open the runtime ruler toolbar).
* In Runtime, click the Stop Updating / Pause button on the TrendControl toolbar.
* Click the Configuration Dialog icon (or access via ruler).
* Under the Time Axis tab:
- Change mode from Current time range to Start and end time (or Fixed time range).
- Set the Start Time to a historical date in the past (e.g., 7 days or 1 month ago).
- Set the End Time to the target historical window.
- Click OK: TrendControl queries the OS Server, which delegates the historical request to Process Historian, rendering the full historical curve.
Configure WinCC AlarmControl for Historical Selection:
* On the AlarmControl toolbar, click the Selection Dialog button.
* Under the Time / Date filter tab:
- Check Time interval.
- Select a historical date range spanning past the 2-day local boundary.
- Click Apply: AlarmControl populates the chronological event list with historical records retrieved from the Process Historian database.

Verifying PH Server Data Packages and OLE DB Provider Authentication

If explicit historical time queries return empty screens with zero data:

Verify Process Historian Assignment in WinCC Explorer:
* On the primary OS Server, open WinCC Explorer.
* In the navigation tree, right-click Process Historian and select Properties.
* Confirm that the Server Name matches the Process Historian computer name and status indicates: Connected / Active.
Verify Server Data Generation on OS Server:
* In WinCC Explorer, right-click Server Data, select Generate.
* Confirm that <OS_Project>_PH.pck is successfully created.
Verify OS Client Server Data Loading:
* On the OS Client project, open Server Data.
* Ensure that the updated server data packages from all OS Servers are imported.
Verify Windows User Group Membership:
* On both OS Server and PH, ensure the Windows user accounts are members of:
- SIMATIC HMI
- SIMATIC BATCH (if batch data is queried)
- Process Historian Administrators.

Verification

Verify historical trend and alarm display:
1. On the OS Client, open WinCC TrendControl.
2. Set the start date to 10 days in the past: Confirm that the trend curve renders smoothly across the entire 10-day span.
3. Use the ruler tool: Verify that exact timestamp and process values can be inspected for data points logged 10 days ago.
4. Open AlarmControl, select the historical chronological view, and filter for events from 14 days ago: Confirm that past alarms and operator acknowledgments populate the grid.

Limitations and Operational Precautions

Querying massive historical datasets (e.g., 100 high-frequency analog trends spanning 1 year) simultaneously can cause transient network spikes and high CPU utilization on Process Historian. Use downsampled or aggregated archive tags for long-term overviews.
Never expand the local OS Server circular archive size beyond 7 to 14 days; doing so bloats the local WinCC SQL database and slows down real-time SCADA screen loading.
Ensure both OS Servers and Process Historian synchronize their system clocks to a common NTP master clock (such as SICLOCK TC 100 / TC 400).

Engineer FAQ

Why can't I see historical data while the TrendControl is in rolling online mode?

In rolling online mode, TrendControl continuously displays the live circulating buffer. To query Process Historian, updating must be paused or the time axis must be explicitly switched to a fixed historical time window.

What happens to historical trends if the Process Historian server goes offline?

While Process Historian is offline, OS Clients can still view the recent 2 days of data from the local OS Server circular cache. Older data becomes temporarily inaccessible until the PH connection is restored.

Can historical alarms and trends be exported to Excel from the OS Client?

Yes. Both WinCC TrendControl and AlarmControl feature export buttons on their runtime toolbars to export displayed historical datasets directly to CSV or XML files.