This code system http://terminology.hl7.org/CodeSystem/action-type defines the following codes:

CodeDisplayDefinition
create CreateThe action is to create a new resource.
update UpdateThe action is to update an existing resource.
remove RemoveThe action is to remove an existing resource.
fire-event Fire EventThe action is to fire a specific event.
 <status value="draft"/> <experimental value="false"/> <date value="2020-04-09T21:10:28+00:00"/> <publisher value="HL7 (FHIR Project)"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> <telecom> <system value="email"/> <value value="fhir@lists.hl7.org"/> </telecom> </contact> <description value="The type of action to be performed."/> <caseSensitive value="true"/> <valueSet value="http://terminology.hl7.org/ValueSet/action-type"/> <content value="complete"/> <concept> <code value="create"/> <display value="Create"/> <definition value="The action is to create a new resource."/> </concept> <concept> <code value="update"/> <display value="Update"/> <definition value="The action is to update an existing resource."/> </concept> <concept> <code value="remove"/> <display value="Remove"/> <definition value="The action is to remove an existing resource."/> </concept> <concept> <code value="fire-event"/> <display value="Fire Event"/> <definition value="The action is to fire a specific event."/> </concept> </CodeSystem>