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2.0 Data FlowData InterfaceData FlowRaw Data - ExampleTurning Off Exception?Compression Test (PI Server)Compression Test – ExampleCompression ResultsSlide 9Data Compression – How Much Data?RecommendationsCopyrights - Trademark statementCopyright © 2005 OSIsoft, Inc.2.0 Data FlowCopyright © 2007 OSIsoft, Inc.Data InterfaceThe data interface is a program which gathers data from a source like a Distributed Control System (DCS) or another data source, such as a PLC or lab system.Copyright © 2007 OSIsoft, Inc.3Data FlowInterface (on DeltaV server)PI ServerPI compression algorithmPIArchivesSnapshotNew value(scan or exception based)Exception ReportException CompressionException reporting is turned off with our systemCopyright © 2007 OSIsoft, Inc.4Raw Data - ExampleRaw values from the control system.Without Exception and Compression tests, these would all be archivedTimeTemperatureCopyright © 2007 OSIsoft, Inc.5Turning Off Exception?Behavior of ExcDev=0, ExcMax= 0 (Exception turned off)All values are sent to PI.This will increase the traffic between the data collection node and the serverTurning off Exception Filtering may be appropriate for many tags and even many entire PI systems, especially if you have: - a smaller total tag count - an efficient and reliable network - a well-tuned data source / industrial control systemCopyright © 2007 OSIsoft, Inc.6Compression Test (PI Server)Compression Test:Last archived value•If a value between the last archive event and the current snapshot is outside the box, the current snapshot violates the compression test. In this case, the value previous to the current snapshot will be archived.•The Compression Test is done by the PI Server•Compression can be turned off with the Compressing attribute+ Compdev- CompdevCurrentsnapshot< Compmax (s)Copyright © 2007 OSIsoft, Inc.7Compression Test – ExampleTimeTemperatureA: Archived ValueAAAAAAAThe compression algorithm is performed on new snapshots to determine which data is kept in the PI archivesCopyright © 2007 OSIsoft, Inc.8Compression ResultsTimeTemperatureWhen the user requests a tag-time for which the value is interpolated, the difference can be no greater than ±compdevValues kept in the PI archivesCopyright © 2007 OSIsoft, Inc.9Compression ResultsRaw values scannedTimeTemperatureAfter ExceptionAfter CompressionCopyright © 2007 OSIsoft, Inc.Data Compression – How Much Data?This highly variable data cannot be compressed by PI. Everyvalue is a pivot point for the “Swinging Door” algorithm. Allvalues are archivedThis data appears highly compressible. Probably only three or four of these values would be stored in the archive.Copyright © 2007 OSIsoft, Inc.11RecommendationsSet the Compression Deviation to the minimum change that is measurable by the instrument.Set the Exception Deviation to ½ of the compression deviationNote: these are starting point recommendations.Note: ExcMin, ExcMax, CompMin and CompMax are in SECONDSCopyright © 2007 OSIsoft, Inc.12Copyrights - Trademark statementPI is a registered trademark of OSIsoft, Inc.Microsoft Windows, Microsoft Windows for Workgroups, and Microsoft NT are registered trademarks of Microsoft Corporation. Solaris is a registered trademark of Sun Microsystems.HP‑UX is a registered trademark of Hewlett Packard Corp. IBM AIX RS/6000 is a registered trademark of the IBM Corporation. DUX, DEC VAX and DEC Alpha are registered trademarks of the Digital Equipment Corporation.Oracle is a registered trademark of Oracle Corporation.© 1997-2006 OSIsoft, Inc. All rights


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