Understanding Delta Query Support
A delta query requests all entities that have been created, changed, or deleted since the prior query. The delta query protocol defines a pull-model protocol for clients to obtain changes in entity sets.
SAP NetWeaver Gateway version 2.0 SP05 and later provides delta query support. OData exposes individual records as entities, and collections of records as entity sets. You can query entire entity sets, which return all entities belonging to the set, or you can specify query filters. For business-object entity sets that contain large amounts of data, filtering provides better performance.