PI connectors data buffering

AVEVA's earlier generations of interface technologies use PI Buffer Subsystem for buffering data. The PI connector framework uses a buffering algorithm that does not require configuration and is always on. It is considered in-process, meaning it is not run as a separate Windows service. Similar to the way buffering works with PI Buffer Subsystem, each Data Archive or PI Asset Framework server for which the connector is configured has its own independent buffer session.

Connector to relay buffering

PI connectors buffer different types of data streams (such as time-series values, assets, and event frames) within a single buffer queue.

In case of a connection loss or network delays, the number of buffered events grows and is flushed once the connection is re-established.

Relay to PI System buffering

PI Connector Relay buffers data to PI System servers. This includes time-series values, tag creation, and asset creation events.

Connector configuration for relay behavior

Relays have specific behaviors in their interactions with Data Archive and PI AF. Some behaviors are configurable. For more information about the behaviors, see the supplemental chapters for Data Archive and PI AF in the PI Connector Administration User Guide.

Buffering statistics

The Buffer Statistics report shows information about data that has been collected but not yet sent to the target destination.

The report lists each destination host and its status, number of buffers, number of errors, and number of messages in the buffer. For relays, PI AF host names are shown with the suffix (AF).

The Buffer Statistics report is useful for determining whether data is being buffered or flowing to the target destination.

Buffer Messages

Buffer messages alert users to errors, identify what is causing errors, and indicate the corrective actions required to resolve errors.

Here, for instance, is a sample buffer error message:

An invalid modification to an existing AF object was attempted. Discarding offending event and continuing processing. ID: SFO.24B0D811-C129-4FD1-8AD1-4EED17D1FBB6. Error details:

It identifies the cause:

Attribute type change

And it describes the corrective action:

Change the attribute type to the "New Type" displayed in the error message, and then restart the connector. For static attributes, this will fix the problem. For data references, changing the attribute type corrects the error, but the underlying PI point will not receive updates because it still has an incompatible type.