Audit Trail

An Audit Trail is a secure, chronological record that provides documented evidence of the sequence of activities that have affected a specific operation or data set. In manufacturing systems like MES, it acts as a digital history, ensuring that every change is transparent and permanent.

The Strategic Importance of Audit Trails

In a digital factory, data is only as good as its traceability. An Audit Trail is the foundation of Data Integrity (ALCOA+). It protects against unauthorized changes and ensures that KPIs, such as OEE, are based on unmanipulated, raw facts.

Essential Requirements: Who, What, When & Why

To be audit-ready and compliant with international standards, an Audit Trail must capture:

1. Who (Identity): The unique user ID of the person performing the action. Shared logins are strictly prohibited in regulated environments.
2. What (Action): The type of change (Create, Update, Delete). For updates, the record must show the original value versus the new value.
3. When (Timestamp): A secure, synchronized system timestamp.
4. Why (Reason for Change): A mandatory comment field for critical actions, explaining the intent behind an override or modification.

Shop Floor Use Cases

• Process Setpoints: Tracking when an operator adjusts a machine parameter (e.g., pressure or speed) and why.
• Downtime Classification: Ensuring transparency when downtime reasons are reclassified to prevent "political" OEE reporting.
• Quality Dispositions: Documenting who authorized the release of a quarantined batch and the data evidence used for that decision.

Common Pitfalls

• Shared User Accounts: Making it impossible to attribute an action to a specific person.
• Editable Audit Trails: If an Audit Trail can be deleted or altered, it loses all legal and quality-related value.
• Lack of "Before/After" Data: Only noting that a change occurred without recording what was actually changed.