Learning about REST APIs > Concurrency control using etags |  | next

# Concurrency control using etags

A client uses etags to verify the version of the resource model. This prevents the client from modifying (`PUT`) a version of the resource model that is not current. For example, if a client performs a `GET` on a server profile and receives an etag in the response header, modifies the server profile, and then updates (`PUT`) the resource model, the etag in the `PUT` request header must match the resource model etag. If the etags do not match, the client `PUT` request will not complete and a `412 PRECONDITION FAILED` error is returned.

prev | up | next
Error message format | home | Developer tools in a web browser

Copyright © 2013-2016 Hewlett Packard Enterprise Development LP