Each application server can operate in the offline mode, thereby providing local survivability in case your data network fails and the application server loses connectivity with the storage server. The offline handling of messages and directory information means that Messaging can continue to provide call-answering service, basic message review, and voice messaging capability.
Offline handling in the Messaging system is session-based and only applies to those users who are affected by the outages in the data network. For example, if the application server connects to more than one storage server and only loses connectivity to one of the storage server, offline handling applies only to the users of the storage server that is offline. Service for users with storage on the operational storage server is unaffected.
The Messaging system is capable of handling local outages because the application server maintains a cache of relevant data, such as:
Directory information (including greetings, recorded names, and relevant setting)
Voice messages
The cache is a hybrid or distributed cache. Directory data is cached on a single application server. Voice messages are stored in a cache that is distributed among the application servers in a cluster.
In an offline mode, users can still use the TUI and access messages that were received in the past three days or as configured. Users can also access any new messages received after the outage began. For information about the features that are temporarily unavailable, see Limitations of local survivability.