Overview of Read-Only and Read-Write interfaces

This document provides information on the differences between Read-Only and Read-Write interfaces, as well as instructions for migrating from the Read-Write to the Read-Only option.

What are the differences between Read-Only and Read-Write?

The Read-Write option enables the configuration of output points, which can be used to write to a data source. However, writing to the data source can cause harmful or unintended results, either accidental or malicious.

The Read-Only option does not include functions for writing to the data source.

Which option is recommended?

The Read-Only option is strongly recommended as an inherently safer technology that also simplifies compliance with security policy. Usually, the Read-Only interface provides all the functionality necessary by gathering data from the data source and sending that data to the PI System.

Do I need the Read-Write option?

If this is a new install and you need to write to the data source, review your security model before using the Read-Write option. Alternatives such as using methods within the data source to safely read and validate data from an external system should be considered, instead of open acceptance of writes from the Read-Write option.

If you already have the interface installed, determine if the interface currently uses output points. To do this, examine the log files that show messages that the interface prints at startup. Each interface prints the number of points loaded by the interface, and specifies the input points and the output points. If the interface currently uses output points, you must use the Read-Write option of the interface for those points.

Note: When output points are required, implement an output point whitelist, which provides a defense against accidental or malicious changes to the data source. See Whitelist output points for a Read-Write interface.

Learn more about PI interfaces

For more information on interfaces, see Overview of PI Interfaces.