Applicable Systems
Wonderware System Platform
Symptoms
The SCADA historian database has stopped logging data. The trend charts show no new data points after the alarm timestamp.
Possible Causes
- Database disk full due to excessive data retention without archiving
- Database service crashed or hung due to memory pressure
- Database connection pool exhausted, preventing new data writes
- OPC DA/AE subscription to the PLC lost
Troubleshooting Steps
- Step 1: Check the database server disk space and free up space if full
Archive or purge old data; set up automatic archiving - Step 2: Verify the database service is running and not in a hung state
Restart the service if it is not responding; check the event log for errors - Step 3: Check the database connection pool usage
Increase the pool size or reduce the number of concurrent clients if exhausted - Step 4: Verify the OPC subscription status in the SCADA configuration
Re-establish the connection if the OPC subscription was lost
How to Reset
Reset: After the database issue is resolved, verify data logging resumes and check trend charts for new data points.
Common Replacement Parts
- Database backup: OEM-specified backup tool (Schedule daily backups)
- Disk space monitor: Windows or Linux built-in (Set alert at 80% full)
Frequently Asked Questions
- Q: How do I check disk space?
On Windows: right-click the database drive in File Explorer. On Linux: use 'df -h'. Set monitoring alerts at 80% full.
- Q: How often should I purge old data?
Depends on the retention policy. Typically, full-resolution data is kept for 30-90 days, then aggregated to 1-minute or hourly averages for long-term storage.
- Q: What causes OPC subscription loss?
Network disconnection, PLC CPU restart, or OPC server crash. SCADA systems should auto-reconnect. Check the reconnect timeout setting.
Source: OEM Technical Manual
Category: SCADA