Abstract: Software rejuvenation techniques which improve reliability of a software system by stopping execution of the system and restarting the execution with "clean" state. The rejuvenation techniques are generally available to applications executing in a computer system. The techniques are implemented using a daemon process which observes applications registered with it and restarts them if they crash or hang and a process like the cron process of the UNIX operating system. The daemon process responds to a rejuvenation specification which indicates that an application which is registerd with it be rejuvenated by making a script for the cron process which specifies that the application's process be killed. When the cron process executes the script and kills the application, the daemon process observes that the application is dead and restarts it. In restarting the application, the daemon process may use state previously saved by the application for that purpose.

Abstract: A channel switching system useful in a satellite for amplifying some or all of three different RF frequency-band channel signals in two traveling wave tube amplifiers and transmitting the signals via two spot antennas to two regions on earth. Two signals are normally amplified in the two amplifiers and directed to the two regions on earth. A third frequency channel signal can be simultaneously applied through one or the other of the two paths. If an amplifier fails, the third frequency channel can be directed through the remaining operative amplifier to either one of the two regions on earth.