Can You Write Data to PI System via PI Web API? A Quick Guide

OSIsoft's PI System is renowned for collecting, storing, and exposing operational data. Traditionally, data ingress to PI has relied on interfaces or connectors. However, questions commonly arise: Can you write data directly into the PI System using a RESTful API instead? Specifically, is the PI Web API read-only, or does it offer write capabilities?

Let's clarify this based on the current state of PI Web API.

Writing Data with PI Web API: What's Supported

Since PI Web API 2015, write operations have been supported in addition to the existing data retrieval (GET) methods.

For PI Point Data

• Endpoint: POST streams/{webID}/value
• Purpose: Write (update) a single current value to a PI Point.
  • Example: Send a POST request with the desired timestamp and value payload to update a tag.
  • Documentation: See the Streams controller - UpdateValue section in the PI Web API help.

For AF Attributes (Static/Configuration Data)

• Endpoint: PUT attributes/{webID}/value
• Purpose: Update the value of a static or configuration AF attribute (not time-series data).
  • Use case: Changing a setpoint or configuration parameter associated with an AF Element.
  • Documentation: See the Attributes controller - UpdateValue in the API docs.

Limitations

• Bulk Writes: At present, bulk write support (writing multiple values in a single request) is not available. Each write action must be performed individually.

Should You Use PI Web API for Ingress Instead of Interfaces?

• Interfaces/Connectors remain the best practice for large-scale, high-frequency data collection from process equipment or standard protocols. They are optimized for robust, reliable, high-volume streaming.
• PI Web API is ideal for ad hoc data injections, integration with applications or custom solutions, and IoT scenarios where data arrives from disparate REST-capable sources.

Conclusion

The PI Web API empowers developers and integrators to both read from and write to the PI System. Whether you're updating live sensor data from a custom device or modifying a digital setpoint, PI Web API puts these capabilities at your fingertips—no interface required.

Always consult the latest PI Web API documentation for up-to-date method details and best practices for security and data integrity.