1.6 Lock-Free Concurrency Control

For applications that work with JSON documents, Oracle extends HTTP entity tag (ETAG) support to implement lock-free, optimistic concurrency control.

A database GET request to True Cache automatically computes the ETAG and inserts it into the returned document. When the modified document is PUT back into the primary database, the following occurs:

1. The database verifies that the underlying document rows still match the ETAG that was computed by the GET request.
2. If the rows match the ETAG, the rows are atomically updated.
3. If there's not a match, another user has changed the data and the PUT request is rejected.
4. The PUT request can be retried using the new data.