Sparkplug NDATA before NBIRTH — Data message received with no birth certificate

A Sparkplug host received an NDATA or DDATA for a node it has no NBIRTH for. Sparkplug metrics are aliased by number, and the alias-to-name map lives in the birth certificate — without it the payload is undecodable.

Start free MQTT / Sparkplug B → canonical

Diagnosis

When you hit this

The host application started after the edge node, so it missed the retained birth message.
The edge node published a birth without the retain flag, so late subscribers never see it.
Broker restart cleared retained messages while edge nodes stayed connected and kept publishing data.

Resolution

How to fix it

Request a rebirth
Publish an NCMD with the Node Control/Rebirth metric set true. A compliant edge node republishes its NBIRTH immediately.
Retain birth certificates
NBIRTH and DBIRTH must be published retained so any host connecting later can decode the stream.
Treat a broker restart as a fleet rebirth
After the broker loses retained state, every edge node needs a rebirth or the data is permanently opaque.

Normalization

What Forge does about it

A request that fails on some points and succeeds on others still normalizes. The tags that arrived resolve to canonical fields as usual; the ones that did not come back are listed in unresolved_tags and excluded from coverage_pct, so a partial read reports as partial instead of quietly looking complete.