Upgrading Citect SCADA to AVEVA Plant SCADA 2026: offline or online, Migration Tool, licensing, server order

Citect SCADA has been called AVEVA Plant SCADA since release 2020 R2, and the current release is Plant SCADA 2026. AVEVA's documentation allows an offline upgrade of a project from any Citect SCADA version from 5.21 onwards, and an online upgrade, with the plant kept running on redundant servers, only from Plant SCADA 2023 or 2023 R2. This article follows the upgrade chapter and release notes of the Plant SCADA 2026 documentation, and adds the checks we make before touching a running system. How a Plant SCADA system is built: AVEVA Plant SCADA architecture, clusters and redundancy.

1. Offline or online: which path fits your version

The 2020 R2 release notes describe the rename, which also changed installation folders and Start menu paths; files such as Citect.ini keep the old name. AVEVA describes two upgrade methods:

Online from an older version means first upgrading temporarily to 2023 or 2023 R2. In both cases AVEVA asks for the latest update on the version you leave, the upgrade to 2026, and then the latest 2026 updates.

2. Prepare: backups, files and the licence

• Projects: back up each project to a .ctz file with Save sub-directories and Save configuration files selected. The Save Included Projects option puts included projects in an "_IncludeProjects" sub-folder; system projects such as Library_Controls are not added. Since 2023 R2, CSV_Include is no longer a system project: if a project is based on the CSV_Include templates, back it up separately, restore it by hand and include it as a user project.
• From 2016 or earlier to 2018 R2 or later: check the [CtEdit]ANSIToOEM parameter in Citect.ini, then run Update Pages with Fast Update Pages disabled before the backup, so that the correct ANSI characters are saved.
• Other files to save: Citect.ini, deployment files, the alarm database of each alarm server, trend files (.HST and .00X), report files, custom ActiveX controls (.OCX), Process Analyst views, specialty drivers in the bin folder, device logs and runtime files named in the [Path] section.
• Licence: the upgrade needs a valid support agreement or a purchased licence upgrade. AVEVA recommends updating the production keys before any project is updated, because the updated key still licenses the previous version.
• Uninstall: remove the old version, and delete its installation folder by hand if it remains.

3. Licensing: Sentinel keys and AVEVA Enterprise Licensing

Plant SCADA 2026 supports two licensing technologies, and the two cannot run on the same computer. Sentinel Licensing, which AVEVA calls legacy, uses USB keys holding the licence type and point count; for a new version the key is updated with CiUSAFE, from the Licensing activity in Plant SCADA Studio, with an authorization code from AVEVA's License Activation page. AVEVA Enterprise Licensing is software based: a browser-based License Manager, a License Server and an online Activation Server. Schneider Electric's Floating License Manager is not supported from Plant SCADA 2023; its users must move to AVEVA Enterprise Licensing.

Licences follow the computer role: server, control client, view-only client or standalone HMI. Both technologies use a Dynamic Point Count of the I/O device addresses used at runtime. The 2026 release notes record a change that can raise it: variable tags from real I/O used in time-stamped digital and analog alarms are now counted.

4. On each computer: install, upgrade, migrate, compile

AVEVA's offline procedure, which an online upgrade also uses on each server:

1. Install Plant SCADA 2026 and check for 2026 updates first, since an update can fix the automated project migration.
2. In Configurator, confirm the System Management Server, encryption and the server password, then close Configurator and restart if asked.
3. Restore the .ctz backups in the Projects activity. Studio forces a project upgrade; [CtEdit]Upgrade set to 1 upgrades all projects.
4. Run the Project Migration Tool (see the table below).
5. Merge project-specific and driver parameters from the old Citect.ini into the new one.
6. Compile. Errors are likely: Cicode functions may have changed or been removed, and the compiler is stricter. Coming from 2018 R2, warning W1041 flags a network address entered as an IP address; for encryption, enter the computer's DNS Name in Topology, Computers.
7. Run the Setup Wizard.
8. Restore runtime files and historical data: delete legacy alarm files such as ALMSAVE.DAT when coming from 2015 or later, keep trend files in the same folder structure, and upgrade a copy, because upgraded files may not work with the old version.
9. Run the project and test I/O communication, alarms and trends before production.

The automatic upgrade only updates database field definitions and copies new files; the Project Migration Tool, under Home in the Project activity, makes the functional changes. The options that matter most on an old project:

An aborted migration is not rolled back; the project is restored from the backup. AVEVA's safety message on these pages: the upgrade alters communication settings, so every I/O device must be checked and adjusted afterwards.

5. Online upgrade of a redundant pair

For an online upgrade from 2023 R2, AVEVA's sequence is:

• On every server, add [LAN]EarliestLegacyVersion = 8500 (8400 when coming from 2023) to Citect.ini and restart, so upgraded servers accept connections from the old version.
• Stop runtime on the primary server and upgrade it as above. Encryption is on by default in 2026: if the old system was not encrypted, set 2026 to Mixed Mode until the upgrade is complete.
• Place the backed-up alarm database in the [CtEdit]Data folder, restart the primary, and wait until its alarm database has synchronised with the running old server.
• Upgrade the clients one by one, with the same server password.
• Stop runtime on the standby server, upgrade it and restart it. When the upgraded server takes the primary role, it converts the whole alarm database to the new format.
• Check the whole system, then switch off the primary to test that the standby takes over.

AVEVA warns against shutting down the upgraded primary before the standby is upgraded, stopping both servers, or starting the old standby while the upgraded primary runs. A side-by-side set of new servers and clients is the other option; it doubles PLC data requests. If the hardware alarm "Redundant Server not found" appears, AVEVA points to that parameter, Networked mode on both servers, the same server password and Mixed Mode. Afterwards remove [LAN]EarliestLegacyVersion.

6. Deployment, drivers and Windows

The deployment architecture changed in Plant SCADA 2023. A 2026 deployment server cannot deploy to computers on 2020 R2 or earlier, so the old deployment server stays until every computer is upgraded.

Since 2020 R2 the installation media carries a reduced set of core drivers; the others come as driver packs from the AVEVA Knowledge & Support Center, installed on the I/O server and on every computer that compiles the project. Plant SCADA 2026 runs on 64-bit Windows 11 LTSC 2024, 25H2 and 24H2, and Windows Server 2025, 2022 and 2019, with .NET Framework 4.8.

7. What the release notes removed

Also in the 2026 notes: AVEVA Historian Plant SCADA Connector 4.0 or earlier cannot log in with a Plant SCADA user password set in 2026; AVEVA recommends Windows authentication there.

What TDL checks before an upgrade

These are our working steps, not AVEVA requirements:

• We read the installed version and update on every computer, and list servers, clients and the deployment server.
• We back up every project, its included projects and the files in AVEVA's list, and restore them on a test computer.
• We list the I/O devices and drivers on each I/O server, including specialty drivers and ABCLX devices.
• We check the licence type, the support agreement and the point count, and each computer's Windows against the 2026 list.
• We upgrade, migrate and compile on the test computer, then choose offline or online for the plant.

When the plant moves to another platform

Some plants replace the PLCs and the SCADA together. At Pha Lai II Thermal Power Plant, TDL migrated the PLC-5 and Citect control systems of the subsidiary plants to ControlLogix and FactoryTalk View SE. Options for older HMI and SCADA: Legacy HMI/SCADA migration paths.

How TDL approaches it

TDL Industrial Automation is a System Integrator in the AVEVA Partner Ecosystem, and builds, extends and maintains applications on AVEVA Plant SCADA (formerly Citect) among other AVEVA platforms. More: AVEVA system integrator in Vietnam, other control system migration and What is AVEVA.