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.
Switching to Memory-based Session Storage
To create such a session the storageType parameter in Session(String, String, ProtocolVersion, Boolean, Session..::.SessionStorageType) constructor has to be set to MemoryBasedStorage value.
Example
bool keepSequenceNumbersAfterLogout = false; Session session = new Session( "SenderCompID", "TargetCompID", ProtocolVersion.FIX42, keepSequenceNumbersAfterLogout, Session.SessionStorageType.MemoryBasedStorage);