PI WebServices update ratio

Discussion created by Bannikov on Nov 14, 2013
Latest reply on Nov 15, 2013 by Bhess

Hello all!


We're developing our very first web applications that uses PI WebServices (2012 version) as a primary and only data source. We use both GetPISnapshotData and GetPIUpdates methods to retrieve fresh updated data from PI/AF Server. GetPISnapshotData is used for complex attributes where no signup for updates is provided. GetUpdates is used for PI Point based attributes (like famous SINOSOID).


I've configured SINUSOID for fast data update (every second with no exception and no compression at all - for testing purposes, of course). I've also configured my application to call GetPIUpdates method every second. So I had expected that every call of GetPIUpdates method gave me about one new value.


Surprisingly, only each fifth call returned with data. First four calls gaves me nothing, and only fifth call gaves me all five values that I had expected. This repeated contantly. So I suppose that it some update ratio in PI WebServices that prevent too fast data retrieve. Seems to be this ratio is about 5 seconds (I remember that ProcessBook has the same default update ratio for all incoming data). Is it true?  If yes, is this update ratio configurable in any ways? Please, can somebody (preferably from OSIsoft) clarify this for me (and my team too). Thank you in advance! Look forward to hear anything about it!