Memory-based session storage is typically used to maintain a high-performance FIX session when persisting of a sessions state and messages to the file system is not required.
The session state and replay history are lost when the process stops. To continue after a restart, reconcile externally maintained state with the counterparty, or agree a sequence reset. See Restoring Session State from Log Files for the procedures and Selecting Storage for Session Messages Logging for persistent storage alternatives.
To create such a session, the storageType parameter in the OnixS::FIX::Session::Session constructor has to be set to the OnixS::FIX::SessionStorageType::MemoryBased value.