Program guide > Access data with the REST data service
Optimistic concurrency
The eXtreme Scale REST data service uses an optimistic locking model by using native HTTP headers: If-Match, If-None-Match, and ETag. These headers are sent in request and response messages to relay an entity's version information from the server to client and client to server.
For more details on Optimistic Concurrency, refer to MSDN Library: Optimistic Concurrency (ADO.NET).
The eXtreme Scale REST data service enables optimistic concurrency for an entity if a version attribute is defined in the entity schema for that entity. A version property can be defined in the entity schema by a @Version annotation for Java™ classes or a <version/> attribute for entities defined using an entity descriptor XML file. The eXtreme Scale REST data service automatically propagates the value of the version property to the client in the ETag header for single entity responses using an m:etag attribute in the payload for multiple entity XML responses, and an etag attribute in the payload for multiple entity JSON responses.
For more details on defining an eXtreme Scale entity schema, see Define an entity schema.
Parent topic:
Access data with the REST data service
Related concepts
Operations with the REST data service
Related reference
Request protocols for the REST data service