The three services, startup and crash recovery, the system tray manager, running without a logged-in user.

MergenHub is installed as three Windows services and a small system-tray manager. Services run in the background under the Local System account, start at boot and keep running when nobody is logged in — an operator PC, a server in a cabinet or a virtual machine all behave the same.

The three services

SCM name	Display name	Process	What stops if it is down
`MergenHub`	MergenHub Runtime (OPC UA + Config API)	`MergenHub.exe`	Everything: device scanning, OPC UA, web UI, REST API, alarms, SCADA
`MergenHubDataBridge`	MergenHub Data Bridge	`MergenHub.IoTGateway.exe`	Outbound MQTT/REST agents and the Data Bridge REST server
`MergenHubHistorian`	MergenHub Historian	`MergenHub.Historian.exe`	Writing tag history (values are still live; nothing is logged)

The two auxiliary services depend on the core service (depend= MergenHub): Windows starts the core first, it writes an internal token, then the others connect to the core over the local REST API. Splitting them into processes means a failure in a cloud connector or a database driver can never take the OPC UA server down.

Settings › Services — status, uptime, restart counters and controls for every runtime service

Startup and crash recovery

All three services are set to Automatic start. On the installer's Service startup behaviour page you can switch to Automatic (delayed) or manual.
Recovery is configured for each service: if the process crashes, Windows restarts it after the delay you chose (default a few seconds). Inside the core, every driver channel runs under a supervisor as well; a dead channel worker is recreated within seconds without restarting the service.
The core also has a runtime restart that restarts the scan engine in-process (used by the trial window and by Settings › Services). It does not touch the Windows service.

Managing services

Settings › Services in the web UI shows each runtime service with start/stop/restart and the auto-restart switch. From an administrator prompt:

sc query MergenHub
sc stop  MergenHub
sc start MergenHub
sc qc    MergenHubHistorian

or with PowerShell: Get-Service MergenHub*, Restart-Service MergenHub.

Note Stopping the core stops the dependent services too; starting the core does not start them automatically until their own start command runs (Windows handles this at boot).

The system-tray manager

MergenHub.Tray.exe is registered to start at logon for all users and sits next to the clock as MergenHub Administration.

Shows the service state (green/yellow/red) and the trial countdown when unlicensed.
Restart runtime — restarts the scan engine in-process (new trial window, reloads drivers) without stopping the Windows service.
Start / Stop / Restart service — the Windows services (requires elevation).
Open web UI, Open data folder, Event log, version and license summary.

The tray application is optional; the services run without it.

Running without a logged-in user

Nothing needs a desktop session. After a reboot the services start and devices are scanned before anyone signs in. Only the tray icon requires a user session.

Resource usage

Memory grows with the tag count: roughly 250–350 MB for a few thousand tags, 2–3 GB at 450K tags with many OPC UA subscribers. CPU is dominated by the drivers' scan rates. Settings › Services and the dashboard show CPU, RAM and disk of the machine; a capacity banner warns when RAM gets tight.

Service accounts and permissions

The services run as Local System by default and need write access to C:\ProgramData\MergenHub. If you switch them to a dedicated account (for example to reach a network share for ODBC logging), grant that account Modify on the data folder and Log on as a service.

Windows Event Viewer

Service start/stop and unhandled crashes are also written to Windows Logs › Application with source MergenHub. MergenHub's own detailed logs are described in Logs and diagnostics data.

Windows services and the tray app