Embodiments that generate checkpoint images of an application for use as warm standby are contemplated. The embodiments may monitor accesses of external references by threads. An external reference may comprise a connection or use of services of an entity that is external to the set of processes that constitute the application, to which a process of the application attempts to connect by means of a socket or inter-process communication (IPC). Various embodiments comprise two or more computing devices, such as two or more servers. One of the computing devices may generate a checkpoint image of an application at a suitable point in time during initialization, when the state of the application is not yet dependent on interactions with external references. The second computing device may preload checkpoint image for the application and activate the checkpoint images when needed, following the specific resource management rules of the distributed subsystem.