Case Study

Water

Two Historians Unified, Eighteen Years of History Preserved

Greater Western Water inherited two independent historian platforms after merger. Parasyn consolidated both onto a single redundant OSI PI platform — migrating 18+ years of operational history, commissioning 18 new servers, and catching two risks that would have been costly to discover at cutover.

Project Reference

GWW / J13423

Handover Date

January 2025

2 to 1

Historians Consolidated

18 Servers

Windows Server 2022

18+ Years

History Preserved

Jan 2025

Cutover Complete

“Merging a decade of Central OSI PI history with almost a decade of Western Wonderware history onto one redundant, correctly-licensed platform — then building the tooling to backfill any gap the merge left behind.”

Project Overview

Following its formation through merger, Greater Western Water (GWW) inherited two independent historian platforms: an OSI PI system serving the Central region with archive data reaching back to March 2015, and a Wonderware Historian (WWH) serving the Western region — Gisborne, Melton, Merrimu, Romsey, Rosslyn and the Western Head Office sites — with data back to 2016. The two systems used different technologies, resided on ageing server infrastructure, and gave GWW no single, common view of its historical operational data.

Parasyn was engaged in April 2024 to consolidate both platforms onto a single upgraded OSI PI instance: migrating Western tag configuration and historical data into PI, upgrading the Central PI environment onto new Windows Server 2022 infrastructure, connecting the Western Citect SCADA systems to the consolidated PI collective through new redundant interface servers, and decommissioning the Wonderware Historian. Cutover to the new platform was completed in January 2025.

Following a successful go-live, GWW requested continued engagement for data-quality optimisation, health-check tooling, extended historical data migration and backfilling capability — work that has continued into 2026 and reflects the trust built during the core delivery.

Technical Scope & Requirements

The scope covered a multi-phase consolidation across two independently operated historian environments, spanning new infrastructure, platform upgrades, data migration, SCADA integration, and post-cutover optimisation.

Data & Licensing Audit

Full audit of both historian platforms' tag counts, data quality and licensing ahead of migration, covering the Central PI AF database and the Western WWH database.

Server Refresh

16 new Central PI servers (primary/standby historian, AF, CoreSight and SQL, in test and production) plus 2 new Western PI interface servers at Sunbury and Rosslyn — all on Windows Server 2022.

Platform Upgrade

Central PI upgraded to OSI PI Data Archive 2018 SP3 Patch 6, the latest AVEVA-supported legacy release, retaining GWW's perpetual licensing model rather than migrating to subscription licensing.

Western Citect-to-PI Integration

New redundant PI interface nodes at Sunbury (primary) and Rosslyn (standby), connected via CT-API directly to the primary and standby Western Citect SCADA servers, replacing WWH as the Western data path.

Historical Data Migration

Western WWH tag configuration and multi-year archive data from 2016 transferred into PI, with the historical archive later extended back to 2008 to give GWW a deeper baseline for trend analysis.

Third-Party Data Flows

FTP integrations with BOM, Ventia, Melbourne Water and DELWP maintained without interruption throughout, with the BOM exchange re-provisioned through PI Web API.

The Challenge — Two Hidden Risks Inside the Merge

Two risks emerged directly from combining two mature, independently operated historians onto one platform. Both were identified and treated through structured engineering — but left unaddressed, either could have significantly disrupted the delivery or compromised the historical record the consolidation was meant to protect.

A Licensing Shortfall Hidden in the Merge

The Western and Central tag counts individually looked unremarkable. But the September 2024 audit showed that adding them together exceeded licensing limits — before accounting for any future growth in Western user demand once the merge made that data more accessible. Left undiscovered, this would have forced an emergency licence purchase at or after cutover.

A Redundancy Design That Did Not Fully Protect

A Western Historian Data Gap Report in October 2025 found that the new redundant PI-Citect interface nodes at Sunbury and Rosslyn were both experiencing short, intermittent communication drops with the Citect SCADA host — typically 15 to 60 seconds — with frequency increasing through 2025, and on occasion both primary and standby nodes affected simultaneously. The redundant pair did not always fully protect against data loss. Because PlantSCADA's own trend buffer retains only around a year of history and has no native backfill capability, gaps beyond that window risked being permanently unrecoverable.

The Parasyn Solution

Both risks were addressed through structured investigation and proactive tooling — turning potential liabilities into documented, reusable capabilities.

Audit Before the Merge

A full data-quality, tag-count and licensing audit of both historians was completed before any migration work began. The shortfall was identified while there was still time to plan for it. Parasyn recommended 40% licensing headroom to absorb future Western user growth rather than licensing to the bare minimum.

Structured Data-Gap Investigation

The Western Historian Data Gap Report correlated PI ICU health-point logs against observed data gaps, characterised the failure pattern, and issued vendor-facing recommendations: a SCADA-side watchdog tag for real-time alerting, evaluation of a modern PlantSCADA connector, and a supported backfill pathway.

Purpose-Built Backfilling Capability

In the absence of native backfill tooling, Parasyn developed and continued to refine a documented, repeatable process including PowerShell scripts that export, cluster-map and consolidate historical trend data from both WWH and PlantSCADA into PIConfig-ready files for bulk import — turning an ad hoc recovery task into a reusable capability.

Ongoing Optimisation Engagement

The quality of the core delivery earned a continued engagement with GWW covering tag cleansing, health-check tooling, extended historical export and additional access and documentation support — all completed post-cutover as discrete, scoped work packages.

Implementation & Cutover Methodology

Planning & Design (Apr - Sep 2024)
Kick-off, Requirements Verification Matrix, full audit of both historian platforms, and detailed design covering topology, firewall rules and server specifications.
Central PI Upgrade
New Windows Server 2022 VMs provisioned at ADC and BDC. OSI PI upgraded to 2018 SP3 Patch 6. Data archive migrated from legacy Central servers.
Western Integration
Two new redundant PI interface servers deployed at Sunbury and Rosslyn, connected via CT-API to the primary and standby Western Citect SCADA servers. Western tag configuration and WWH archive data transferred into PI.
Cutover & Proving Period (Jan 2025)
Western Citect data redirected to the new PI collective, with legacy servers kept available for reversion through a minimum 60-day trouble-free proving period ahead of decommissioning.
Post Go-Live Optimisation (Feb 2025 - Aug 2026)
Tag cleansing, health-check tooling, data-gap investigation and resolution, extended historical tag export, and development of documented, repeatable backfilling procedures.

Project Outcomes & Status

As at August 2026, cutover to the consolidated PI platform is complete and stable. The legacy Western Wonderware Historian application has been decommissioned. Parasyn continues to support GWW through data-quality optimisation work.

✓

Two Historians Unified

Central PI and Western WWH consolidated onto a single redundant OSI PI platform — giving GWW common access to historical data across both regions for the first time.

↑

18+ Years of History Preserved

Western tag configuration and multi-year archive transferred into PI, later extended back to 2008 for deeper historical trend analysis. Third-party data flows to BOM, Ventia, Melbourne Water and DELWP maintained without interruption.

★

Backfilling Capability Delivered

A documented, repeatable PowerShell-based process for exporting and re-importing historical trend data from both legacy and current SCADA platforms — a reusable capability for any future historian gap.

Standards & Frameworks Applied

SEMP — Audit report, detailed design, Requirements Verification Matrix and change request register applied throughout to manage a technically interdependent, multi-phase consolidation.

OSI PI / CT-API / OPC-HDA — Platform and protocol standards governing the SCADA-to-historian interfaces across both the Western Citect and Central Geo SCADA environments.

Lessons Learned & Future Recommendations

Insight	Impact & Context	Recommendation
Licence Ahead of the Merge, Not After	Auditing both platforms before migration caught a licensing shortfall while there was still time to plan for it.	Complete a full tag-count and licensing audit of both source platforms before committing to a migration architecture.
Redundancy Needs Failure-Mode Testing, Not Just Design	The Western PI-Citect interfaces were architected for redundancy, but the data-gap investigation showed correlated, simultaneous drops on both primary and standby nodes.	Validate failover pairs against network-level failure modes, not just individual hardware failure, before go-live.
Build Backfilling Capability Proactively	Developing a documented, repeatable backfill process turned an ad hoc recovery task into a reusable capability for any future historian gap.	Develop and test a backfill process for every historian migration before cutover, not after a gap is discovered.
Plan for the Tail	Tag cleansing, health-check tooling and extended historical export all delivered well after formal cutover.	Budget post-go-live optimisation as a distinct phase on historian consolidation projects, not as an afterthought.

Site

Greater Western Water — historian upgrade and consolidation across Central and Western regions