matthew.rivett return archived value?

Discussion created by matthew.rivett on Jan 9, 2012
Latest reply on Jan 9, 2012 by Ahmad Fattahi

I recently inserted data into the archive using piconfig using the following...




@table piarc


@mode create,t


@modify mode=replace


@istru tag,time,value


tag1,08-Nov-2011 09:56,532.9147


tag2_kv,08-Nov-2011 09:56,No Data


tag3,08-Nov-2011 09:56,No Data


Inserting the data into the archive caused a program using to see the archived value.  I see in the manual that using eventpipes this could happen but I do not see anything about data.snapshot.  Is this expected?




Applications which need to monitor each value for a tag as it changes on the server will want to use this EventPipe. However, this eventpipe monitors all new snapshot and archive edit events for the point. Not all the events in this eventpipe show up in the snapshot of the point. Only events with timestamp greater than or equal to the current snapshot value will replace the current snapshot. Hence, if the application is only interested in new events, it needs to always check the timestamp of the events and to trap out of sequence events.