The Coherence call-state storage facility for Converged Application Server is built on the distributed cache service of WebLogic Server. In each managed server in the domain cluster, Coherence combines logic and processing with state-storage data. Coherence writes data to the primary partition cache-storage server and it, in turn, writes a backup copy to the configured number of backup copies.

See "Understanding Distributed Caches" in Developing Applications with Oracle Coherence for an explanation of Coherence distributed caches.

The image below illustrates an administration server with a Coherence cluster for call-state storage.

The Coherence call-state storage facility includes the following features:

• Built-in support for dynamically adding or removing nodes
• Partitions that migrate dynamically, eliminating the need to configure replica servers and their partitions
• Enhanced data serialization with Portable Object Format (PoF)
• Proven node death detection for fail-over and split brain handling
• Flexible configuration
• Advanced network protocol that leverages UDP and supports multi-cast to optimize network usage
• Graceful migration of partitions from one node to another during startup and shutdown, limiting the impact on ongoing traffic and reducing the risk of overload