Synchronizing and Resetting Process Historian Metadata After WinCC Tag Logging Changes

In SIMATIC Process Historian (PH 2014 SP2 / PH 2020), deleting or renaming tag logging archive folders in WinCC does not automatically delete corresponding archive containers in Process Historian because regulatory compliance (FDA 21 CFR Part 11) prohibits silent purging of historical metadata. To clean up deleted archive folders and re-synchronize metadata, disconnect the OS Server via the Process Historian Ready (PH-Ready) Configuration Tool, clear the local cache under C:\ProgramData\Siemens\ProcessHistorianReady, set the OS project to Maintenance Mode in the Process Historian Management Console (PH-MC), and re-bind the project container. For non-production testing environments, a complete clean database reset can be executed via the Database Installation Wizard.

Executive Summary

Enterprise data warehousing in SIMATIC PCS 7 relies on SIMATIC Process Historian (PH) to aggregate long-term process values and alarms from distributed OS Servers. During commissioning, automation engineers frequently modify WinCC Tag Logging configurations—such as renaming archive folders, relocating tags between custom archives and the SystemArchive, or deleting obsolete measuring points. While changes appear immediately in local WinCC Runtime trend curves, engineers discover that Process Historian continues to display the obsolete archive folders alongside the new structures. Attempting to manually purge SQL tables risks database corruption. This article explains the append-only schema architecture of Process Historian, outlines metadata synchronization mechanics, and details approved maintenance workflows.

Architecture and Fundamental Mechanics

Process Historian Relational Schema Architecture, PH-Ready Synchronization, and Metadata Immutability:

The Immutability Principle in Industrial Archiving:
Process Historian is engineered for high-integrity long-term data preservation conforming to international pharmaceutical and power generation audit standards.
Its underlying Microsoft SQL Server relational database (HISTORIAN_STORAGE) operates on an append-only model.
When an OS Server registers an archive folder (e.g. TES_Heat), PH creates an entry in its metadata dictionary tables (dbo.Archive, dbo.Tag). Even if that folder is deleted from the WinCC engineering project, PH retains the metadata entry to guarantee that any historical data already logged under that identifier remains queryable in future audits.
How Metadata Is Replicated via PH-Ready:
The background service SIMATIC Process Historian Ready (CCProcessHistorian.exe / PHReadyService.exe) on each OS Server monitors the local WinCC Tag Management and Tag Logging SQL databases.
When archive structures change, PH-Ready pushes incremental metadata updates over TCP port 4224.
If an engineer deletes a folder and recreates tags under SystemArchive, PH-Ready registers the new associations, but does not issue SQL DROP or DELETE commands to PH.
Methods for Re-aligning Metadata:
Method A: Maintenance Mode Synchronization: Placing the project in Maintenance Mode via PH-MC allows PH to mark the deleted archive as detached/inactive, hiding it from default Information Server reporting views.
Method B: Testing Environment Database Re-initialization: On staging or testing systems, the Process Historian Database Installation Wizard (DatabaseInstallationWizard.exe) can re-initialize the HISTORIAN_STORAGE instance, wiping all test data and establishing a clean baseline matching the final Tag Logging layout.

Step-by-Step Implementation Procedure

Align WinCC Tag Logging on the OS Server:
* In WinCC Explorer, open Tag Logging.
* Confirm that the final desired archive structure is established (e.g. all process tags assigned to SystemArchive).
* Save and close Tag Logging.
Clear Local PH-Ready Cache on the OS Server:
* Open Windows Services (services.msc); stop the SIMATIC Process Historian Ready service.
* Open Windows File Explorer; navigate to:
C:\ProgramData\Siemens\ProcessHistorianReady\.
* Delete the temporary cached project container files (.xml metadata caches).
* Restart the SIMATIC Process Historian Ready service.
Update Project Status in Process Historian Management Console (PH-MC):
* Log onto the Process Historian server as Administrator.
* Open Process Historian Management Console from the Siemens Automation start menu.
* Navigate to Management > Projects.
* Select the OS Server project; click Maintenance Mode.
* Allow PH to reconcile archive metadata with the incoming PH-Ready package.
* Switch the project status back to Active.
Procedure for Complete Database Reset (Commissioning / Staging Only):
* If the plant is in pre-commissioning and all historical test data can be discarded:
* On the PH server, launch Process Historian Database Installation Wizard from Siemens Automation > Process Historian.
* Select Initialize Database (or recreate database instance).
* Follow the wizard to format a fresh HISTORIAN_STORAGE database.
* Once initialized, re-connect the OS Server; PH will ingest the clean Tag Logging configuration without obsolete folders.

Verification

In Process Historian Management Console, navigate to Diagnostics > Data Ingestion; confirm that the OS Server status is green ('Active').
Open SIMATIC Information Server in a web browser; launch the Tag Browser.
Confirm that the deleted folder (TES_Heat) no longer appears in the active tag tree and that all tags under SystemArchive display real-time trend data.

Limitations and Operational Precautions

Never execute SQL DROP TABLE or DELETE scripts directly against the HISTORIAN_STORAGE database using SQL Server Management Studio. Manual SQL tampering invalidates database consistency checks and can permanently corrupt archive segmentation.

Engineer FAQ

Why doesn't deleting an archive folder in WinCC delete it in Process Historian?

Process Historian uses an append-only architecture conforming to FDA 21 CFR Part 11; it retains historical metadata to preserve historical data integrity.

How do I clear obsolete metadata from Process Historian during testing?

Clear the PH-Ready cache on the OS Server and re-synchronize via Maintenance Mode, or re-initialize the database using the Database Installation Wizard.