Revise the alarms-over-gateway plan based on review feedback:
The gateway is for MxAccess (live data + Galaxy hierarchy); the
Wonderware historian sidecar is for aahClientManaged (time-series +
alarms historian). Two SDKs, two concerns. Routing alarm-historian
write-back through the gateway would force coupling that doesn't need
to exist — the sidecar already has a dormant WriteAlarmEvents IPC slot
ready to wire.
Drop A.5 (gateway WriteHistorianEvent RPC). Add Track C — two PRs in
the historian sidecar that complete the dormant slot:
C.1 AahClientManagedAlarmEventWriter implementation
C.2 Program.cs wires the writer into HistorianFrameHandler
B.4 reverses from "delete the IPC slot" to "consume the IPC slot" via
a new SidecarAlarmHistorianWriter on the lmxopcua side.
Also tightens Why-section #3 + D5 to make explicit that the path is
exclusively for non-Galaxy alarm producers (scripted alarms today, AB
CIP ALMD or others future). Galaxy-native alarms reach AVEVA Historian
via System Platform's own HistorizeToAveva toggle, independent of
anything in our stack.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Joseph Doherty
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