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OPC UA Property to TAG Example (limit as example)

This page explains how to ingest OPC UA point Properties into TDengine supertable TAG columns through taosX. It uses limit as an example, but the same workflow applies to other Property names.

When to use this​

  • Your OPC UA server defines business metadata as Properties under Variable nodes (for example limit, EngineeringUnits, upperBound)
  • You want taosX to map these Properties into TAG columns automatically

Key rules​

  1. The attribute must be a Property of the target Variable (HasProperty), not an independent data point.
  2. In Explorer task configuration, prefer:
    • Node Class: all
    • Root Node ID (optional): set it to a parent path that includes the target Variable to narrow scan scope; if omitted, browsing usually starts from the server default root
  3. Avoid name collisions between custom_tags and Property names.

Example: ingest limit as TAG​

OPC UA node layout example​

Objects
└── Plant
    └── Area1
        └── Sensor01
            └── Temperature                              (Variable)
                ├── limit = "0~100"                      (Property)
                └── EngineeringUnits = "degree Celsius"  (Property)

In Select Data Points mode, use:

  • Root Node ID (optional): for example ns=2;i=3 (use your actual address space; values differ across servers)
  • Node Class: all
  • Super Table Name: opc_limit_{type} (example only)
  • Table Name: t_{ns}_{id#/_}
  • Timestamp: received_ts

Fill connection/authentication fields based on your real OPC UA environment.

Validation steps​

USE <target_db>;
SHOW STABLES;
DESCRIBE <stable_name>;

You should see TAG columns that match the actual Property names on your server, for example:

  • limit VARCHAR(1024) TAG
  • EngineeringUnits VARCHAR(1024) TAG

Then verify values:

SELECT tbname, `limit`, `EngineeringUnits`
FROM <stable_name>
LIMIT 5;

Is limit a special keyword?​

No. limit is only an example name. As long as the server models metadata as OPC UA Properties under the Variable, other names (for example high_limit, alarmLevel, unit) can be mapped to TAG columns in the same way.

Troubleshooting​

1) Only custom_tags are present, but Property TAGs are missing​

Check:

  • Root Node ID is appropriate (optional, but recommended for large address spaces)
  • Node Class is all
  • The source attribute is truly modeled as a Property (not a normal Variable)

2) New TAGs do not appear after config updates​

If the supertable already exists with an old schema, TAG columns are not auto-backfilled. Create the task with a new database/table name, or drop/recreate the old schema and rerun.