Abstract: A back-up system for a computer program running within a network of servers. Multiple instances of the program are installed and configured, each on a different server. The configuration generates an “environment” for each instance, which is an entity required for the instance to run. One (or more) instances are selected as the active instances, and they run; the others remain dormant. The environments of the active instances are backed up to storage which is shared by all servers. If an active instance fails, its environment is copied from the storage to a dormant instance, which then becomes active. This transition process is vastly faster than one alternative, namely, installing another instance from scratch.