Interface buffering overview

The interface node uses buffering to prevent data loss when Data Archive is not available. UniInt interfaces can buffer data to store point values when network communication to Data Archive is unavailable. UniInt disconnected startup requires buffering, and it is highly recommended for failover. Buffering for interfaces is configured and enabled through PI ICU.

The PI System offers two services to implement buffering at interfaces. Only one of them, PI Buffer Subsystem, supports buffering for clients. For more information about buffering, see the PI Interface Configuration Utility User Guide.

• PI Buffer Subsystem (pibufss)

  PI Buffer Subsystem is the best option for most environments, particularly version 4.3 or later. Starting with version 4.3, PI Buffer Subsystem supports buffering to multiple servers and collectives. For information about configuring this buffering service, and the considerations for using PI Buffer Subsystem 4.3 or later, see PI Interface Configuration Utility User Guide.

If the interface is properly configured with buffering, the interface service cannot run unless the buffering service is also running.

Note: Correct interface service dependencies are a common troubleshooting point. Ensure the interface service dependencies for the buffering service are configured correctly.

Without buffering running during a loss of connection to Data Archive, any data collected while the connection is unavailable is permanently lost.

Buffering and collectives

PI Buffer Subsystem 4.3 and later can buffer data to multiple independent servers, including those configured as PI Server collectives. For interfaces to use PI Buffer Subsystem with PI Server collectives, the Data Archive servers must be running PI Data Archive version 3.4.375 or later.

Buffering configuration

Use PI Interface Configuration Utility (PI ICU) to configure interface buffering.

The Tools > Buffering option helps you configure buffering. Depending on your current configuration, this option does one of the following:

• If this computer is configured to buffer data using PI Buffer Subsystem 4.3 or later, the Buffering Manager window opens and shows a buffering dashboard. The dashboard shows information about the status of buffering on this computer.

• If this computer is not currently configured to buffer data, and PI Buffer Subsystem 4.3 or later is installed, you are prompted to configure PI Buffer Subsystem. If you click Yes, the Buffering Manager window opens and shows the installation wizard, which helps you configure PI Buffer Subsystem.

• If this computer is configured to buffer data using API Buffer Server (Bufserv), and PI Buffer Subsystem 4.3 or later is installed, you are prompted to convert to and configure PI Buffer Subsystem. If you click Yes at both prompts, the Buffering Manager window opens and shows the upgrade wizard, which helps you upgrade from API Buffer Server to PI Buffer Subsystem.

• If PI Buffer Subsystem 4.3 is not yet installed, the Buffering window opens for API Buffering or the earlier version of PI Buffer Subsystem.

For PI Buffer Subsystem 4.3, when configuring an interface to buffer data to a PI Data Archive server which has not been added to the buffered server list you must enable buffering. Click the Enable button in the Buffering Status box on the interface General page. To verify that the buffering status is On, exit PI ICU, then restart and select the interface.

You can use Buffering Manager to configure, monitor, and troubleshoot buffering using PI Buffer Subsystem. PI Buffer Subsystem is recommended for applications connecting to PI Data Archive 3.4.375 or later.