HL7 NMD_N02 (Application Management Data) | Integration Soup HL7 Reference Guide

HL7 NMD_N02 Application Management Data

An application tells another system about its clock, statistics, or status without being asked first.

HL7 message structure NMD_N02 groups and segments from HL7 v2.5.1 Hide structure

These are the generated groups and segments for the version selected at the top of the page. The article explains the workflow, and this panel follows the chosen HL7 version.

Message Structure

Segment	Name	Required	Repeatable
MSH	Message Header	Yes	No
SFT	Software Segment	No	Yes
NMD_N02.CLOCK_AND_STATS_WITH_NOTES	Clock And Stats With Notes group	Yes	Yes
NMD_N02.CLOCK	Clock group	No	No
NCK	System Clock	Yes	No
NTE	Notes and Comments	No	Yes
NMD_N02.APP_STATS	App Stats group	No	No
NST	Application control level statistics	Yes	No
NTE	Notes and Comments	No	Yes
NMD_N02.APP_STATUS	App Status group	No	No
NSC	Application Status Change	Yes	No
NTE	Notes and Comments	No	Yes

NMD_N02 is an unsolicited application management data message. It is not patient traffic. It is operational traffic: a system reports clock data, statistics, or status changes to a receiver that monitors applications.

You might see it around older HL7 interface engines, device gateways, lab systems, or high-availability setups where one application needs to tell another that it is up, down, switching hosts, or reporting counters.

A small NMD N02 example

MSH|^~\&|HL7GATEWAY|CITYHOSP|MONITOR|CITYHOSP|20260718121500||NMD^N02^NMD_N02|NMDN020001|P|2.5.1 NCK|20260718121500 NTE|1||Interface host clock synchronized before maintenance window. NST|Y|HL7GATEWAY01|APP|20260718000000|20260718121500|120000|118900|4321|4310|0|0|1 NSC|DOWN|CPU-A|FS1|HL7GATEWAY^CITYHOSP|CITYHOSP

What systems do with it

The sender pushes operations data to a monitoring receiver. The receiver records the state, updates dashboards, alerts operations staff, or correlates the status change with interface traffic.

A common workflow is an application warning that it is going down for backup or maintenance, or that it has switched processing to another CPU or file server. The receiving system should acknowledge the NMD_N02 with a normal ACK.

How to read the structure

MSH identifies NMD^N02^NMD_N02. The repeating management group can include NCK for clock data, NST for application statistics, and NSC for application status changes. NTE can add explanatory notes after each part.

Not every group has to contain all three data types. A sender may report only a clock, only statistics, only status, or a combination depending on the event.

Implementation traps

Do not route NMD_N02 through patient-message rules. It should be monitored and secured as operational telemetry, not filed to a chart.

Also agree what the NSC change codes mean. "DOWN", "UP", "SWITCH", and similar values only help if both systems use the same local vocabulary and alert policy.

Reference notes

HL7 describes NMD_N02 as an unsolicited application management data message. The refactored HL7 page gives examples such as an application going down for backups or switching CPU/file-server resources. See NMD_N02.