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General

Data Flow Problems

Diagnose and fix issues with data not appearing or being delayed.

No Data Appearing

Symptoms

  • UNS Explorer shows no values
  • Device detail page "Latest Values" tab is empty
  • Dashboards show "No Data"

Diagnostic Steps

Verify Device is Active

Navigate to Data Management > Devices and ensure:

  • The device shows a green connection indicator
  • The Active checkbox is enabled

Check Gateway Status

The gateway must be Connected to relay data. See Gateway Not Connecting.

Validate Protocol Configuration

For PLC protocols (Modbus, Siemens, OPC UA):

  • Verify IP address and port
  • Check credentials if required
  • Confirm the PLC is powered on and reachable

Inspect System Logs

Filter logs by Category = Proxus.ProtocolDrivers to see protocol-specific errors:

  • Read failed - Communication timeout
  • Invalid register - Incorrect tag address

Data is Delayed

Symptoms

  • Values in the dashboard are seconds/minutes behind real-time
  • Timestamps show old data

Common Causes

CauseSolution
High polling intervalReduce the Polling Interval in device profile (e.g., 1000ms instead of 5000ms)
Slow database writesCheck ClickHouse/PostgreSQL performance; consider increasing batch size
Network latencyVerify stable connection between gateway and central server
Store-and-Forward activeIf the gateway was offline, buffered data is replayed in order
info
Store-and-Forward

When a gateway loses connection, it stores data locally and forwards it when reconnected. This is expected behavior and ensures no data loss.

Data Quality Issues

Duplicate Values

If you see repeated identical values:

  • Change Detection may be disabled - enable it in the device profile
  • PLC may be returning stale values - check PLC scan cycle

Missing Tags

If some tags appear but others don't:

  1. Verify tag addresses in the device profile
  2. Check for typos in register names (e.g., DB1.DBD0 vs DB1.DBW0)
  3. Ensure tag data types match the PLC (e.g., Double vs Int)

Incorrect Values

IssueLikely Cause
Large unexpected numbersByte order mismatch (Big Endian vs Little Endian)
All zerosTag address incorrect or PLC not responding
Negative values when expecting positiveSigned vs Unsigned data type mismatch

Database Write Failures

Symptoms

  • Log shows: ❌ Worker batch processing failed
  • Data accumulates in memory but isn't persisted

Solutions

  1. Check Database Connection

    # Test ClickHouse connectivity
curl http://<clickhouse-ip>:8123/?query=SELECT%201

  2. Verify Credentials: Check Proxus-config.toml for correct database connection string (see Reference)

  3. Monitor Disk Space: Full disk will cause write failures

  4. Review Batch Size: Very large batches may timeout; reduce if needed

warning
Data Loss Prevention

If database writes fail repeatedly, the platform will buffer data in memory. Restart after fixing the issue to flush the buffer.

See Also

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Gateway Issues
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Rules & Automation