You can take an active application out of the loop using a controlled failover.
SipContainerMBean is used to initiate a server quiesce through wsadmin (command line interface). This MBean is used to set the container's weight to 0, which prevents new messages from being routed to it.
WebSphere® Application Server PMI is used to monitor the server's active sessions. The remaining active sessions can be watched by enabling a counter on the server being quiesced. The server can be shut down once the number of active sessions reaches an acceptable level. A script can be written to monitor active sessions and shut down the server when an acceptable threshold is achieved.