PI data replication

In a steady state, AVEVA™ PI System Connector 3 (PSC3) subscribes for changes on the source Data Archive, and collects snapshot and archived events. Archived events are collected for source PI points that have compression enabled/on as indicated by the PI point attribute compressing=1.

Snapshot events are collected for source PI Points that satisfy a Snapshot Query under the Overview tab, regardless of the compressing setting of the PI point attribute.

Note: PSC3 does not replicate data collection for future PI points, nor data collection for Blob PI point types.

PSC3 replicates all data events from source to destination. In some situations, however, perfectly identical archives are not possible. For example, there is a possibility that snapshot values are returned and sent to the destination PI System when retrieving archive only data (such as a recorded values call). A call to retrieve recorded values (also known as compressed values) from the source PI System includes the snapshot value if the snapshot value timestamp falls within the range requested in the recorded values call. This is a standard PI System behavior and occurs regardless of the requested call used to retrieve recorded values.

During the start of data collection, PSC3 replicates PI point configuration from the source PI System to the destination PI System. By default, PI point compression is set to off, compressing=0, for all PI points on the destination PI System unless the PI point matches a defined snapshot query for the source Data Archive. As a result, values transferred from the source PI System that have compressing=0 bypass the compression algorithm on the destination PI System and are archived.