Storage for Session State Data

Storing session state data enables the session state to be recovered after the failover of a server instance in a cluster. Recovering the session state enables the session to continue without loss of information. Communications Server provides the following types of high availability storage for HTTP/SIP session and stateful session bean data:

• In-memory replication on other servers in the cluster

In-Memory Replication on Other Servers in the Cluster

In-memory replication on other servers provides lightweight storage of session state data without the need to obtain a separate database. This type of replication uses memory on other servers for high availability storage of HTTP/SIP session and stateful session bean data. Clustered server instances replicate session state in a ring topology. Each backup instance stores the replicated data in memory. Replication of session state data in memory on other servers enables sessions to be distributed.

The use of in-memory replication requires the Group Management Service (GMS) to be enabled. For more information about GMS, see Group Management Service.

If server instances in a cluster are located on different machines, ensure that the following prerequisites are met:

• To ensure that GMS and in-memory replication function correctly, the machines must be on the same subnet.

• To ensure that in-memory replication functions correctly, the system clocks on all machines in the cluster must be synchronized as closely as possible.