Buffering types  

Buffering queues data from PI interface nodes and client nodes in case the PI Server receiving the data becomes unavailable for any reason. For example, this might occur during a network outage, maintenance, or backup.

When the connection with the PI Server or PI collective is restored, the buffering service sends all the stored data from the buffer to the PI Server in the order it was received.

There are three types of data writes that can be buffered:
PI API
Data from PI API applications is usually buffered using PI Buffer Subsystem. If you send buffered data to PI Server version 3.4.370 or older, or if your interfaces run on a non-Windows platform, you need to use API Buffer Server.
PI SDK
Data from PI SDK applications can be buffered only using PI Buffer Subsystem. PI SDK buffering was introduced with PI SDK 2010 R2.
AF SDK
Data from AF SDK applications can be buffered only using PI Buffer Subsystem. AF SDK buffering was introduced with PI Asset Framework 2014 (2.6).
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