OData V2 Part 1: The Classic OData V2 Service Model

📌 KEY POINTS
✅ OData V2 is still everywhere: SEGW services, many standard Fiori apps, older UI5 and integrations.
✅ V2 URLs live under /sap/opu/odata/sap/<SERVICE>/; RAP can also publish V2 bindings.
✅ Syntax differs from V4: $inlinecount=allpages, substringof(), JSON wrapped in "d".
💡 New RAP services use V4; use V2 only for consumers that require it.

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▶ WHAT THIS SERIES COVERS

• Part 1 — the classic OData V2 service model (this lesson)
• Part 2 — deep insert, batch and navigation design
• Part 3 — production troubleshooting with gateway logs and metadata

Related: SAP Gateway series (the runtime behind V2 services).

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▶ 1. WHERE YOU MEET V2

• Services built with transaction SEGW (Gateway Service Builder).
• Many SAP-delivered Fiori apps and older custom UI5 apps (sap.ui.model.odata.v2.ODataModel).
• Integrations written years ago.
• RAP service bindings of type "OData V2 – UI" or "OData V2 – Web API" for consumers that cannot use V4.

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▶ 2. URL AND CONTRACT

• Service root: /sap/opu/odata/sap/ZPURCHREQ_SRV/ (SEGW) or the binding URL for RAP V2.
• $metadata: EntityType, EntitySet, Association, AssociationSet, NavigationProperty, FunctionImport — and SAP annotations (sap:label, sap:creatable, sap:filterable…).
• Keys: /PurchaseRequestSet('4711') or /PurchaseRequestSet(RequestID='4711',Year='2026').

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▶ 3. V2 QUERY OPTIONS

• $select, $filter, $orderby, $top, $skip, $expand — like V4 but simpler ($expand without nested options).
• $inlinecount=allpages — total count in the response (V4: $count=true).
• Functions: substringof('chair',Description) (V4: contains), startswith, endswith.
• Dates in filters: datetime'2026-09-01T00:00:00'.

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▶ 4. JSON FORMAT
Responses (with $format=json or Accept: application/json) are wrapped in "d":
{ "d": { "results": [ … ], "count": "57" } } for lists; { "d": { … } } for single entities, with "metadata" (uri, type, etag).

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▶ 5. OPERATIONS

• CRUD: GET, POST, PUT (full update) and MERGE/PATCH (partial update), DELETE.
• Function imports for operations (V4: actions/functions).
• CSRF token required for writes (same as V4).

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▶ 6. V2 VS V4 (WHAT CHANGES FOR YOU)

• V4: cleaner JSON, contains(), $count, nested $expand options, bound actions, better batch.
• V2: mature tooling, many existing apps; function imports instead of actions.
• Migration of a consumer from V2 to V4 means changing the UI5 model and request syntax — plan it as a project.

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▶ STEP BY STEP

1. Open an existing V2 service in /IWFND/GW_CLIENT (or a browser) and read $metadata.
2. Run the V2 queries in the code example.
3. Compare the same query against the RAP V4 service.

✅ CHECKPOINT: you can read and query any SAP OData V2 service.

A new developer familiar only with RAP V4 tried to add a filter to an old SEGW-based integration using contains(Description,'chair') and $count=true. The service returned errors, and he suspected a broken backend.
A colleague showed him the V2 equivalents — substringof and $inlinecount=allpages — and the "d" wrapper in responses. The integration worked immediately. The team then added a V2/V4 cheat sheet to their wiki, since both protocols would coexist for years.

• Using V4 syntax against V2 services (contains, $count).
• Forgetting the "d" wrapper when parsing V2 JSON.
• Using PUT for partial updates (overwrites unspecified fields).
• Not requesting JSON ($format=json / Accept header).
• Building new RAP services as V2 without a consumer reason.

• Know which protocol a consumer uses before writing requests.
• Read $metadata and SAP annotations (sap:creatable, sap:filterable) first.
• Use MERGE/PATCH for partial updates.
• Offer V2 bindings for RAP services only when consumers need them.
• Plan V2→V4 migrations deliberately.

Questions: "What are differences between OData V2 and V4?", "Where do SAP OData V2 services come from?", "How do you get a total count in V2?"
Strong answer: V2 services come from SEGW, standard apps and RAP V2 bindings, under /sap/opu/odata/sap/; syntax differences: $inlinecount=allpages vs $count, substringof vs contains, "d"-wrapped JSON, function imports vs actions, MERGE vs PATCH, simpler $expand. New RAP services should use V4 unless a consumer requires V2.