Alert
AL00322 - Potential data corruption on source PI Data Archive when using the PI to PI Interface
2017-06-22

Summary

When using the PI to PI Interface, if the destination PI Data Archive becomes unavailable, data from the source PI Data Archive can be written back to the source PI Data Archive. This issue only happens when buffering on the PI to PI interface's machine is enabled for both the source and destination PI Data Archives (or PI Data Archive collectives).

It is unusual to configure buffering for the source PI Data Archive on the PI to PI interface's machine. However, if other interfaces on the PI to PI Interface's machine write to the source PI Data Archive, then you be buffering to the source server. The diagram below shows normal data flow for the aforementioned scenario.

st-widget-{image: AL00322_normal_diagram.png}

When the connection to the destination PI Data Archive is lost, the data flow is altered as shown in the diagram below.

st-widget-{image: AL00322_abnormal_diagram.png}
Although the PI to PI interface is installed on a separate machine in the diagram above, it does not matter where the PI to PI interface is installed. If the buffer the PI to PI interface sends data to is configured to send data to both the source and destination PI Data Archives, then the issue will occur.

Cause

This issue is caused by a bug in the PI API, so both the PI Buffer Subsystem and the API Buffer Server are affected.

Affected Versions

  • PI to PI Interface v3.9.0.42 and earlier
  • PI API 1.6.8.22 and earlier

Refer to Known issues:

Solution

The best solution is to update the PI API. The issue was fixed in version 1.6.8.26 of the PI API. You can download the patch here.

If you cannot update the PI API, then do not enable buffering to the source PI Data Archive on the PI to PI interface's machine. You may need to put the PI to PI Interface on its own machine to accomplish this.