OData Channel
In SAP Gateway, entities are defined and connected in data models. These data models can be exposed as OData services during runtime. Runtime processing is handled by data provider classes (DPC) that are assigned to the object models.
The OData Channel (ODC) for SAP Gateway allows you to develop content by defining object models and registering a corresponding runtime data provider class. There are two ODC application components, the business data provider and the metadata provider. An ODC data provider implements a single interface that is very close to the OData protocol. OData Channel applications obtain access to common framework services, for example, logging or transaction handling using a set of agents called “Common Service Exposure”. These agents wrap existing framework services in a way that OData Channel applications can easily consume.
For SAP NetWeaver systems lower than SAP NetWeaver 7.4, you need to install the software component IW_BEP either on the SAP Gateway system or on the SAP Business Suite backend system. For SAP NetWeaver 7.4 systems and higher, the component SAP_GWFND is installed as standard and includes the functional scope of IW_BEP. For more information about the SAP Gateway components required, see Deployment Options.
Content Programming Model
SAP Gateway enables the content implementation to use OData features. As such, the content inherits the flexibility and complexity of OData.
The provided metadata reflects the implementation of the business data APIs.
OData provides a wide range of request features such as “inlining/expand”, batches, paging, sorting, and filtering. The content implementation balances between the flexibility offered by OData and the technical constraints of the business functionality used.
Customizing
SAP Gateway supports multiple SAP backend systems as providers of OData content. Since OData content can be provided by multiple SAP systems, you must configure the connectivity between the SAP backend systems and the SAP Gateway system.
If multiple SAP backend systems are connected to a single SAP Gateway system, the SAP Gateway system resolves potential service name conflicts.
For example: Many customers have local HR systems in an international system landscape. These local systems may contain identical SAP Gateway content that is exposed by one SAP Gateway system. SAP Gateway provides the flexibility to provide specific URLs for the resources derived out of the SAP Gateway content.
For information on the customizing activities which are available for OData Channel, see OData Channel Configuration.
Note that services can only be processed if SAP Gateway has been activated globally.
To activate SAP Gateway,
access the SAP Implementation Guide (IMG) in transaction
SPRO and navigate to 
SAP NetWeaver 
SAP Gateway OData Channel Configuration Activate or Deactivate SAP Gateway 
.