An organization publishes a map image layer to ArcGIS Enterprise that references data from a user- managed PostgreSQL geodatabase. The schema of a…

When a map image layer is published to ArcGIS Enterprise, it captures the schema of the source data at that moment. This schema is stored within the service definition and is used by the service to draw the map and respond to requests. Subsequent changes to the underlying database schema, such as adding a new field, are not automatically detected by the running service. Restarting the service only reinitializes the existing service configuration; it does not re-read the source data's schema. To incorporate the schema change, the service must be overwritten with a new definition based on the updated data source.

B. The ArcGIS Enterprise portal is a client of the map service. If the new field is not exposed in the service's REST endpoint, the portal has no way to access or display it.
C. Schema locking prevents schema changes on the source data while a service is running. Re-enabling it would not help the service recognize a change that has already occurred.
D. There is no "enterprise geodatabase cache" that, when cleared, would cause a map service to re-read its source schema. The service's schema is fixed at the time of publishing.

1. Esri ArcGIS Pro Documentation

"Overwrite a map service": "You may need to overwrite a map service to reflect changes in the source data

such as updating the data's schema... Overwriting the service is the only way to update the service with these changes."

Source: https://pro.arcgis.com/en/pro-app/latest/help/sharing/overview/overwrite-a-map-service.htm (Accessed under the main section "Overwrite a map service").

2. Esri ArcGIS Enterprise Documentation

"What is a map service?": "When you publish a map service

the server exposes the contents of your map document to others... The map service makes maps

features

and attribute data available to client applications." This implies the service is a snapshot of the map document at the time of publishing.

Source: https://enterprise.arcgis.com/en/server/latest/publish-services/windows/what-is-a-map-service.htm (Accessed under the section "What can you do with a map service?").

3. Esri ArcGIS Enterprise Documentation

"Schema locking": "Schema locking prevents you from changing the schema of a dataset or class while it is in use... If you need to make changes to a dataset's schema

the lock must be released." This document explains the purpose of schema locking

confirming it is a preventative measure

not a tool for updating a service's awareness of schema changes.

Source: https://enterprise.arcgis.com/en/portal/latest/use/schema-locking.htm (Accessed under the main section "Schema locking").