See the related docs of the FHIR Configuration Management API:

https://docs.intersystems.com/irisforhealthlatest/csp/docbook/fhir-config-rest-api/index.html

FHIR Server QuickStart Tutorial

See the Native SDK for Java - here are the specific Docs for manipulating Globals as you asked (but the API provides other access types).

There are some related Open Exchange apps - native-api-command-line-java by @Robert Cemper and native-api-contest-template by @Bob Kuszewski you can also use as samples.