[ERSSUP-81706]-[]-[Swapped endpoints to return 503s rather than 504s]-[JW]

nhsd-jack-wainwright · nhsd-jack-wainwright · commit 8e0ed3bfd5eb · 2025-03-11T13:52:24.000Z
diff --git a/sandbox/src/mocks/r4/NHSDigital-OperationOutcome-503.json b/sandbox/src/mocks/r4/NHSDigital-OperationOutcome-503.json
@@ -6,12 +6,12 @@
     "issue": [
       {
         "severity": "error",
-        "code": "timeout",
+        "code": "transient",
         "details": {
           "coding": [
             {
               "system": "https://fhir.nhs.uk/CodeSystem/http-error-codes",
-              "code": "REC_GATEWAY_TIMEOUT"
+              "code": "REC_UNAVAILABLE"
             }
           ]
         }
diff --git a/sandbox/src/mocks/stu3/STU3-ServiceUnavailable.json b/sandbox/src/mocks/stu3/STU3-ServiceUnavailable.json
@@ -8,13 +8,13 @@
     "issue": [
       {
         "severity": "error",
-        "code": "timeout",
+        "code": "transient",
         "details": {
           "coding": [
             {
               "system": "https://fhir.nhs.uk/STU3/CodeSystem/eRS-APIErrorCode-1",
-              "code": "GATEWAY_TIMEOUT",
-              "display": "Gateway Timeout"
+              "code": "SYSTEM_UNAVAILABLE",
+              "display": "System Unavailable"
             }
           ]
         }
diff --git a/specification/components/r4/schemas/endpoints/a030-retrieve-business-functions.yaml b/specification/components/r4/schemas/endpoints/a030-retrieve-business-functions.yaml
@@ -111,5 +111,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/r4/schemas/endpoints/a033-retrieve-healthcare-service.yaml b/specification/components/r4/schemas/endpoints/a033-retrieve-healthcare-service.yaml
@@ -67,5 +67,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/r4/schemas/endpoints/a035-search-for-healthcare-services.yaml b/specification/components/r4/schemas/endpoints/a035-search-for-healthcare-services.yaml
@@ -77,5 +77,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/r4/schemas/endpoints/a037-retrieve-healthcare-service-version.yaml b/specification/components/r4/schemas/endpoints/a037-retrieve-healthcare-service-version.yaml
@@ -64,5 +64,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/r4/schemas/endpoints/a040-retrieve-practitioner-info.yaml b/specification/components/r4/schemas/endpoints/a040-retrieve-practitioner-info.yaml
@@ -55,5 +55,5 @@
           $ref: '../responses/TooManyRequests.yaml'
         '500':
           $ref: '../responses/InternalServerError.yaml'
-        '504':
-          $ref: '../responses/GatewayTimeout.yaml'
+        '503':
+          $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/r4/schemas/endpoints/a041-search-service-request.yaml b/specification/components/r4/schemas/endpoints/a041-search-service-request.yaml
@@ -79,5 +79,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/r4/schemas/endpoints/a042-retrieve-attachment.yaml b/specification/components/r4/schemas/endpoints/a042-retrieve-attachment.yaml
@@ -95,5 +95,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/r4/schemas/headers/response/RetryAfter.yaml b/specification/components/r4/schemas/headers/response/RetryAfter.yaml
@@ -0,0 +1,6 @@
+description: |
+  Defines a period (in seconds) after which the client should attempt their request again.
+required: false
+schema:
+  type: string
+  example: '120'
diff --git a/specification/components/r4/schemas/responses/ServiceUnavailable.yaml b/specification/components/r4/schemas/responses/ServiceUnavailable.yaml
@@ -1,20 +1,23 @@
 description: |
-  Where status code 504 (Gateway Timeout) is returned then an [NHSDigital-OperationOutcome](https://fhir.nhs.uk/StructureDefinition/NHSDigital-OperationOutcome) will be included in the body, as detailed below.
-  In response to receiving this status code, it is recommended that clients retry at a later time.
-  
-  | issue.details.coding.code | issue.code | Coding System                                                      | Description                                                                                    |
-  | ------------------------- | ---------- | ------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------- |
-  | REC_GATEWAY_TIMEOUT       | timeout    | [BaRS Error Code](https://fhir.nhs.uk/CodeSystem/http-error-codes) | A request to an internal component timed out whilst attempting to serve a response.            |
+  Where status code 503 (Service Unavailable) is returned then an [NHSDigital-OperationOutcome](https://fhir.nhs.uk/StructureDefinition/NHSDigital-OperationOutcome) will be included in the body, as detailed below.
+  In response to receiving this status code, it is recommended that clients retry at a later time based on a returned `Retry-After` header when provided.
+
+  | issue.details.coding.code | issue.code | Coding System                                                      | Description                                                                                                                          |
+  | ------------------------- | ---------- | ------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------ |
+  | REC_UNAVAILABLE           | transient  | [BaRS Error Code](https://fhir.nhs.uk/CodeSystem/http-error-codes) | A request to an internal component timed out whilst attempting to serve a response or the system is currently otherwise unavailable. |
+
 headers:
   X-Correlation-ID:
     $ref: '../headers/response/CorrelationID.yaml'
   X-Request-ID:
     $ref: '../headers/response/RequestID.yaml'
   Content-Type:
     $ref: '../headers/response/ContentTypeFhirJson.yaml'
+  Retry-After:
+    $ref: '../headers/response/RetryAfter.yaml'
 content:
   application/fhir+json:
     schema:
       $ref: '../NHSDigital-OperationOutcome.yaml'
     example:
-      $ref: '../../examples/NHSDigital-OperationOutcome-504.json'
+      $ref: '../../examples/NHSDigital-OperationOutcome-503.json' 
diff --git a/specification/components/stu3/schemas/endpoints/a004-retrieve-reference-data.yaml b/specification/components/stu3/schemas/endpoints/a004-retrieve-reference-data.yaml
@@ -93,5 +93,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a005-retrieve-referral-request-versioned.yaml b/specification/components/stu3/schemas/endpoints/a005-retrieve-referral-request-versioned.yaml
@@ -90,5 +90,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a005-retrieve-referral-request.yaml b/specification/components/stu3/schemas/endpoints/a005-retrieve-referral-request.yaml
@@ -138,5 +138,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a006-retrieve-attachment.yaml b/specification/components/stu3/schemas/endpoints/a006-retrieve-attachment.yaml
@@ -102,5 +102,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a007-retrieve-clinical-information.yaml b/specification/components/stu3/schemas/endpoints/a007-retrieve-clinical-information.yaml
@@ -73,5 +73,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a008-retrieve-worklist.yaml b/specification/components/stu3/schemas/endpoints/a008-retrieve-worklist.yaml
@@ -180,5 +180,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a010-patient-service-search.yaml b/specification/components/stu3/schemas/endpoints/a010-patient-service-search.yaml
@@ -87,5 +87,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a011-create-referral.yaml b/specification/components/stu3/schemas/endpoints/a011-create-referral.yaml
@@ -111,5 +111,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a012-maintain-referral-letter.yaml b/specification/components/stu3/schemas/endpoints/a012-maintain-referral-letter.yaml
@@ -144,5 +144,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a013-accept-referral.yaml b/specification/components/stu3/schemas/endpoints/a013-accept-referral.yaml
@@ -72,5 +72,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a014-reject-referral.yaml b/specification/components/stu3/schemas/endpoints/a014-reject-referral.yaml
@@ -99,5 +99,7 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml' 
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
   '504':
     $ref: '../responses/rejectReferral/504Response.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a015-retrieve-appointment-slots.yaml b/specification/components/stu3/schemas/endpoints/a015-retrieve-appointment-slots.yaml
@@ -80,5 +80,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a016-book-or-defer-appointment.yaml b/specification/components/stu3/schemas/endpoints/a016-book-or-defer-appointment.yaml
@@ -106,6 +106,8 @@ responses:
   '500':
     $ref: '../responses/InternalServerError.yaml'
   '502':
-    $ref: '../responses/bookOrDeferAppointment/502Response.yaml'      
+    $ref: '../responses/bookOrDeferAppointment/502Response.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
   '504':
     $ref: '../responses/bookOrDeferAppointment/504Response.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a019-generate-patient-letter.yaml b/specification/components/stu3/schemas/endpoints/a019-generate-patient-letter.yaml
@@ -52,5 +52,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a020-upload-file-to-document-store.yaml b/specification/components/stu3/schemas/endpoints/a020-upload-file-to-document-store.yaml
@@ -99,5 +99,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a021-create-referral-request-and-send-for-triage.yaml b/specification/components/stu3/schemas/endpoints/a021-create-referral-request-and-send-for-triage.yaml
@@ -82,5 +82,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a022-cancel-appointment-action-later.yaml b/specification/components/stu3/schemas/endpoints/a022-cancel-appointment-action-later.yaml
@@ -109,5 +109,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a023-retrieve-a&g-worklist.yaml b/specification/components/stu3/schemas/endpoints/a023-retrieve-a&g-worklist.yaml
@@ -79,5 +79,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a024-retrieve-advice-and-guidance-versioned.yaml b/specification/components/stu3/schemas/endpoints/a024-retrieve-advice-and-guidance-versioned.yaml
@@ -67,5 +67,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a024-retrieve-advice-and-guidance.yaml b/specification/components/stu3/schemas/endpoints/a024-retrieve-advice-and-guidance.yaml
@@ -109,5 +109,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a025-retrieve-advice-and-guidance-conversation.yaml b/specification/components/stu3/schemas/endpoints/a025-retrieve-advice-and-guidance-conversation.yaml
@@ -116,5 +116,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a026-send-a&g-response.yaml b/specification/components/stu3/schemas/endpoints/a026-send-a&g-response.yaml
@@ -107,5 +107,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a027-convert-a&g-to-referral.yaml b/specification/components/stu3/schemas/endpoints/a027-convert-a&g-to-referral.yaml
@@ -112,5 +112,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a028-record-triage-outcome.yaml b/specification/components/stu3/schemas/endpoints/a028-record-triage-outcome.yaml
@@ -133,5 +133,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a029-available-actions-for-user-list.yaml b/specification/components/stu3/schemas/endpoints/a029-available-actions-for-user-list.yaml
@@ -97,5 +97,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a031-change-shortlist.yaml b/specification/components/stu3/schemas/endpoints/a031-change-shortlist.yaml
@@ -120,5 +120,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a032-change-shortlist-and-send-for-triage.yaml b/specification/components/stu3/schemas/endpoints/a032-change-shortlist-and-send-for-triage.yaml
@@ -100,5 +100,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a036-cancel-referral.yaml b/specification/components/stu3/schemas/endpoints/a036-cancel-referral.yaml
@@ -163,5 +163,7 @@ responses:
     $ref: '../responses/InternalServerError.yaml'
   '502':
     $ref: '../responses/cancelReferral/502Response.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
   '504':
     $ref: '../responses/cancelReferral/504Response.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a038-retrieve-appointment-versioned.yaml b/specification/components/stu3/schemas/endpoints/a038-retrieve-appointment-versioned.yaml
@@ -68,5 +68,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a038-retrieve-appointment.yaml b/specification/components/stu3/schemas/endpoints/a038-retrieve-appointment.yaml
@@ -109,5 +109,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a043-retrieve-advice-and-guidance-overview-pdf.yaml b/specification/components/stu3/schemas/endpoints/a043-retrieve-advice-and-guidance-overview-pdf.yaml
@@ -82,5 +82,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/endpoints/a044-create-advice-and-guidance-request.yaml b/specification/components/stu3/schemas/endpoints/a044-create-advice-and-guidance-request.yaml
@@ -94,5 +94,5 @@ responses:
     $ref: '../responses/TooManyRequests.yaml'
   '500':
     $ref: '../responses/InternalServerError.yaml'
-  '504':
-    $ref: '../responses/GatewayTimeout.yaml'
+  '503':
+    $ref: '../responses/ServiceUnavailable.yaml'
diff --git a/specification/components/stu3/schemas/headers/response/RetryAfter.yaml b/specification/components/stu3/schemas/headers/response/RetryAfter.yaml
@@ -0,0 +1,6 @@
+description: |
+  Defines a period (in seconds) after which the client should attempt their request again.
+required: false
+schema:
+  type: string
+  example: '120'
diff --git a/specification/components/stu3/schemas/responses/ServiceUnavailable.yaml b/specification/components/stu3/schemas/responses/ServiceUnavailable.yaml
diff --git a/specification/components/stu3/schemas/responses/bookOrDeferAppointment/504Response.yaml b/specification/components/stu3/schemas/responses/bookOrDeferAppointment/504Response.yaml
diff --git a/specification/components/stu3/schemas/responses/cancelReferral/504Response.yaml b/specification/components/stu3/schemas/responses/cancelReferral/504Response.yaml
diff --git a/specification/components/stu3/schemas/responses/rejectReferral/504Response.yaml b/specification/components/stu3/schemas/responses/rejectReferral/504Response.yaml
diff --git a/specification/components/stu3/schemas/responses/updateAppointment/504Response.yaml b/specification/components/stu3/schemas/responses/updateAppointment/504Response.yaml

Original file line number	Diff line number	Diff line change
`@@ -6,12 +6,12 @@`
`6`	`6`	`"issue": [`
`7`	`7`	`{`
`8`	`8`	`"severity": "error",`
`9`		`- "code": "timeout",`
	`9`	`+ "code": "transient",`
`10`	`10`	`"details": {`
`11`	`11`	`"coding": [`
`12`	`12`	`{`
`13`	`13`	`"system": "https://fhir.nhs.uk/CodeSystem/http-error-codes",`
`14`		`- "code": "REC_GATEWAY_TIMEOUT"`
	`14`	`+ "code": "REC_UNAVAILABLE"`
`15`	`15`	`}`
`16`	`16`	`]`
`17`	`17`	`}`
Original file line number	Diff line number	Diff line change
`@@ -8,13 +8,13 @@`
`8`	`8`	`"issue": [`
`9`	`9`	`{`
`10`	`10`	`"severity": "error",`
`11`		`- "code": "timeout",`
	`11`	`+ "code": "transient",`
`12`	`12`	`"details": {`
`13`	`13`	`"coding": [`
`14`	`14`	`{`
`15`	`15`	`"system": "https://fhir.nhs.uk/STU3/CodeSystem/eRS-APIErrorCode-1",`
`16`		`- "code": "GATEWAY_TIMEOUT",`
`17`		`- "display": "Gateway Timeout"`
	`16`	`+ "code": "SYSTEM_UNAVAILABLE",`
	`17`	`+ "display": "System Unavailable"`
`18`	`18`	`}`
`19`	`19`	`]`
`20`	`20`	`}`